Porous fiber

ABSTRACT

The present invention provides a nanoporous fiber being substantially free from coarse pores and having homogeneously dispersed nanopores, unlike conventional porous fibers. A porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, and the pores are unconnected pores, or a porous fiber has pores each having a diameter of 100 nm or less, in which the area ratio of pores each having a diameter of 200 nm or more to the total cross section of the fiber is 1.5% or less, the pores are connected pores, and the fiber has a strength of 1.0 cN/dtex or more.

TECHNICAL FIELD

The present invention relates to a porous fiber which has a multitude offine and even-sized nanopores and is substantially free from coarsepores that reflect visible radiation. It also relates to a polymer alloyfiber serving as a precursor of the porous fiber in the productionthereof, and to a method for producing the polymer alloy fiber.

In the following descriptions relating to the present invention, theterm “nanopores” means fine pores each having a diameter of 100 nm orless.

The term “nanoporous fiber” used in the present invention refers to afiber containing one or more pores having a diameter of 100 nm or lessper square micrometer at cross section of a fiber perpendicular to theaxial direction thereof.

The fiber relating to the present invention has such a multitude of finepores and thereby exhibits dramatically increased liquid adsorptivityand/or gas adsorptivity.

To achieve these properties satisfactorily, key factors are that theresulting fiber is substantially free from not-fine, i.e., coarse poresand that the fiber contains a multitude of fine pores in even-sized andhomogeneously distributed at cross section of a fiber.

The present invention relates to a porous fiber standing at such ahigher level than conventional porous fibers. This fiber not onlyexhibits dramatically increased liquid adsorptivity and/or gasadsorptivity as described above, but is also capable of having a varietyof functions by applying the nanoporous structure of the fiber.

Namely, the fiber can be applied not only to the fiber industry but alsoto a variety of industries and is very revolutionary and useful.

BACKGROUND ART

Fibers of polyamides typified by nylon 6 (hereinafter may be referred toas “N6”) and nylon 66 (hereinafter may be referred to as “N66”) andfibers of polyesters typified by a polyethylene terephthalate(hereinafter may be referred to as “PET”) and a polybutyleneterephthalate (hereinafter may be referred to as “PBT”) exhibitexcellent mechanical properties and/or dimensional stability and arewidely used not only for clothing but also for interior decoration,vehicular interior decoration and industrial use.

Fibers of polyolefins typified by a polyethylene (hereinafter may bereferred to as “PE”) and a polypropylene (hereinafter may be referred toas “PP”) are light-weighted and are widely utilized for industrial use.

However, in any kind of fibers, fibers each comprising a single polymerhave some limitations in the properties thereof. Attempts have thereforebeen made to modify such polymers typically by copolymerization orpolymer blending or to compound functions typically by multi-componentfiber spinning or combined-filament spinning.

Among them, polymer blending has been actively investigated, since thistechnique does not require new designing of polymers and such a polymerblend can be produced by using a mono-component spinning machine.

Separately, hollow fibers and porous fibers have been investigated inorder to reduce the weight of fibers or to impart water-adsorptivitythereto.

Attempts have been made to provide hollow fibers having high hollowness,but such hollow portions may be crushed, for example, as a result offalse twisting. To avoid this, multi-islands hollow fibers, wherein amultitude of islands parts constitutes a hollow portion, using aconjugated fiber with a water-soluble polymer have been developed. Insuch fibers, the hollow portion generally has a diameter of 1 μm ormore, the interface between the polymer and the air in the hollowportion significantly reflects visible radiation, and the resultingfiber cannot satisfactorily develop a color.

Porous fibers each having a multitude of pores on the order ofsub-micrometers have been investigated. Such porous fibers havegenerally been produced not by multi-component fiber spinning but bypolymer blend spinning.

Japanese Unexamined Patent Publication (Kokai) No. 2-175965, forexample, describes a technique of blending a nylon with a PETcopolymerized with a hydrophilic group, forming a fiber from the blend,and dissolving off the copolymerized PET from the fiber,to therebyobtain a porous nylon fiber. The fiber of the invention has surfacedepressions and protrusions and/or pores on the order of submicrometersand has pearly luster. However, this fiber shows significantlydeteriorated color property. This is because the fiber has a multitudeof pores having a size on the order of wavelengths of visible radiationand thereby invites significant scattering of visible radiation even ascompared with the multi-islands hollow fiber.

Japanese Unexamined Patent Publication (Kokai) No. 56-107069 (pages 1-3)describes a fiber having pores with a size smaller than visibleradiation. In actual fact, however, the resulting fiber also showssignificantly deteriorated color property, since the blend fibercontains coarsely aggregated PET particles, and the aggregated particlesare dissolved off to form coarse pores each having a size on the orderof submicrometers to one micrometer. In fact, above-mentioned JapaneseUnexamined Patent Publication (Kokai) No. 56-107069 describes “most ofthe polyester component exists as lines with a diameter of 0.01 to 0.1micron and there remain hollows substantially having the above-mentionedsize in the polyamide” in line 7, in the left upper column of page 2,suggesting the presence of aggregated PET particles.

In addition, certain porous fibers using a nylon/PET blend fiber aredescribed in Japanese Unexamined Patent Publication (Kokai) Nos.8-158251 and 8-296123. These fibers, however, show a large variation insize of dispersed particles of PET in the nylon, for example, about 0.1to 1 μm and cannot improve decreased color property caused by coarsepores. In addition, when the distribution of pore size is large as inthe conventional techniques, coarse pores play an extremely increasedrole in the pores and, in contrast, nanopores do not play such a role.Thus, the porous fiber does not sufficiently exhibits advantages of thepores.

Demands have therefore been made to provide porous fibers substantiallyfree from such coarse pores.

Separately, a variety of polymer alloy fibers serving as precursors forporous fibers and ultrafine yarns have been investigated.

U.S. Pat. No. 4,686,074 (page 28), for example, describes that anultrafine PET fiber having a size of 9.4×10⁻⁵ deniers is obtained usinga static mixer according to calculations and discloses a polymer alloyfiber having an islands-in-sea structure and comprising a polystyrene(hereinafter may be referred to as “PS”) as a sea part and PET asislands parts.

This document, however, mentions that an actually measured mono-filamentfineness of the ultrafine PET fiber varies from 1×10⁻⁴ deniers to 1×10⁻²deniers, showing that the resulting polymer alloy fiber includesdispersed particles of the islands parts PET with a diameter of 100 to1000 nm and thus contains many coarse islands.

Japanese Unexamined Patent Publication (Kokai) No. 8-113829 (pages 1-12)discloses a very special polymer alloy fiber comprising a copolyesterblended with 30% by weight of a polyether imide (hereinafter may bereferred to as “PEI”), which copolyester comprises PET copolymerizedwith 10% by mole of an ethylene naphthalate component. In this fiber,PEI is dispersed as particles with a size on the order of 2 to 80 nm.The fiber, however, invites unstable spinning to thereby obtain yarnswith large unevenness and lacks practical utility, because PEI isdispersed as particles in the fiber.

According to the invention disclosed in above-mentioned JapaneseUnexamined Patent Publication (Kokai) No. 8-113829, spinning is carriedout at a temperature of 320° C. in accordance with the melting point ofPEI, which is excessively high for the copolyester, to thereby causeremarkable thermal decomposition. In an experiment for corroboration,the resulting polymer alloy fiber has a strength less than 1.5 cN/dtexand is not usable in practice. The invention disclosed in JapaneseUnexamined Patent Publication (Kokai) No. 8-113829 also provides aspongy fiber having pores connected with each other by treating thepolymer alloy fiber with a base in a 6% NaOH solution at 90° C. for 2hours. The resulting yarn, however, has a strength less than 0.5 cN/dtexand is not practically usable from this viewpoint of strength, becauseboth PEI and the copolyester have been hydrolyzed in the fiber.

DISCLOSURE OF INVENTION

Under these circumstances, a first object of the present invention is toprovide a nanoporous fiber having a multitude of nanopores which arevery homogeneously dispersed and are substantially free from coarsepores, in contrast to conventionally investigated porous fibers.

To achieve the first object, the present invention provides, in anaspect, a porous fiber containing pores each having a diameter of 100 nmor less, in which the area ratio of pores each having a diameter of 200nm or more to the total cross section of the fiber is 1.5% or less, andthe pores are unconnected pores.

Alternatively, the present invention provides, in another aspect toachieve the first object, a porous fiber containing pores each having adiameter of 100 nm or less, in which the area ratio of pores each havinga diameter of 200 nm or more to the total cross section of the fiber is1.5% or less, the pores are connected pores, and the fiber has astrength of 1.0 cN/dtex or more.

A second object of the present invention is to provide a yarn, cutfiber, felt, package, woven fabric, knitted fabric or nonwoven fabricusing the nanoporous fiber having a multitude of nanopores which arevery homogeneously dispersed and are substantially free from coarsepores, in contrast to conventionally investigated porous fibers asmentioned above, or to provide various applied products using these,such as clothing, clothing materials, products for interior, productsfor vehicle interior, livingwares, industrial materials and medicaldevices (hereinafter these are generically referred to as “fibrousarticles”).

To achieve the second object, the present invention provides, in anaspect, a fibrous article containing the porous fiber in the firstaspect of the present invention which has pores each having a diameterof 100 nm or less, in which the area ratio of pores each having adiameter of 200 nm or more to the total cross section of the fiber is1.5% or less and the pores are unconnected pores, alone or incombination with one or more other fibers.

Alternatively, the present invention provides, in another aspect toachieve the second object, a fibrous article containing the porous fiberin the second aspect of the present invention which has pores eachhaving a diameter of 100 nm or less, in which the area ratio of poreseach having a diameter of 200 nm or more to the total cross section ofthe fiber is 1.5% or less, the pores are connected pores and the fiberhas a strength of 1.0 cN/dtex or more, alone or in combination with oneor more other fibers.

The porous fibers according to the present invention are substantiallyfree from coarse pores that cannot be avoided in conventional porousfibers. In other words, the porous fibers of the present invention arenanoporous fibers having very homogeneously dispersed nanopores. Thesenanoporous fibers serve to significantly improve color property ascompared with conventional porous fibers to thereby obtain high-valueadded fibrous articles utilizing excellent moisture adsorption andadsorption properties.

A third object of the present invention is to provide a novel polymeralloy fiber which serves as a material fiber for the production of theporous fibers of the present invention.

To achieve the third object, the present invention provides a polymeralloy fiber having an islands-in-sea structure and comprising a lowersoluble polymer as a sea part, and a higher soluble polymer as islandsparts, the islands constituting a lined structure, in which the arearatio of islands each having a diameter of 200 nm or more to the totalislands is 3% or less.

A fourth object of the present invention is to provide pellets that issuitably used for the production of the novel polymer alloy fiber whichis, in turn, used for the production of the porous fibers of the presentinvention.

To achieve the fourth object, the present invention provides pellets ofa polymer alloy comprising a polyamide and a polyester, in which adispersed polymer component is dispersed in an average diameter of 1 to50 nm.

Alternatively, the present invention provides, in another aspect toachieve the fourth object, pellets of a polymer alloy comprising apolyamide and a polyester, containing 30 to 90% by weight of a polyestercopolymerized with 1.5 to 15% by mole of a sulfonate and having anaverage weight per pellet of 2 to 15 mg.

In addition, the present invention provides, yet another aspect toachieve the fourth object, pellets of a polymer alloy, comprising apolymer selected from polyamides, polyesters and polyolefins; and apolyetherester being soluble in hot water, in which the content of thepolyetherester is 10 to 30% by weight, and the pellets have a b value asan indicator of coloring of 10 or less.

A fifth object of the present invention is to provide a method, formelt-spinning the novel polymer alloy fiber that serves as a materialfiber for the production of the porous fibers of the present invention.

To achieve the fifth object, the present invention provides, in anaspect, a method for melt-spinning a polymer alloy fiber, comprising thesteps of weighing and feeding a lower soluble polymer and a highersoluble polymer independently to a twin-screw extrusion-kneader, meltingand blending the polymers in the twin-screw extrusion-kneader to form apolymer alloy, and melt-spinning the polymer alloy, in which thespinning is carried out so as to satisfy the following conditions (1) to(3):

-   -   (1) the content of the higher soluble polymer in the polymer        alloy is 5 to 60% by weight;    -   (2) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2; and    -   (3) the length of a kneading section of the twin-screw        extrusion-kneader is 20 to 40% of the effective length of        screws.

Alternatively, the present invention provides, in another aspect toachieve the fifth object, a method for melt-spinning a polymer alloyfiber, comprising the steps of weighing and feeding a lower solublepolymer and a higher soluble polymer independently to a static mixerhaving a number of splits of 100×10⁴ or more, melting and blending thepolymers in the static mixer to form a polymer alloy, and melt-spinningthe polymer alloy, wherein the spinning is carried out so as to satisfythe following conditions (4) and (5):

-   -   (4) the content of the higher soluble polymer in the polymer        alloy is 5 to 60% by weight; and    -   (5) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2.

In addition, the present invention provides, in yet another aspect toachieve the fifth object, a method for melt-spinning a polymer alloyfiber, comprising storing and dry-blending two or more different pelletscomprising a lower soluble polymer and a higher soluble polymer,respectively, in a blending tank before melting of the pellets, feedingthe dry-blended pellets to a melting section, and blending andmelt-spinning the dry-blended pellets, wherein the spinning is carriedout so as to satisfy the following conditions (6) to (8):

-   -   (6) the content of the higher soluble polymer in the fiber is 5        to 60% by weight;    -   (7) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2; and    -   (8) the blending tank can contain 5 to 20 kg of pellets.

The attached drawings will be described below.

FIG. 1 is a transmission electron micrograph showing a cross section ofa nanoporous fiber according to after-mentioned Example 1 of the presentinvention.

FIG. 2 is a transmission electron micrograph showing a longitudinalsection of the nanoporous fiber according to after-mentioned Example 1of the present invention.

FIG. 3 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 1 of the present invention.

FIG. 4 is a transmission electron micrograph showing an example of alongitudinal section of the polymer alloy fiber according toafter-mentioned Example 1 of the present invention.

FIG. 5 is a transmission electron micrograph showing an example of across section of pellets of a polymer alloy according to after-mentionedExample 1 of the present invention.

FIG. 6 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 4 of the present invention.

FIG. 7 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example4 of the present invention.

FIG. 8 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 8 of the present invention.

FIG. 9 is a transmission electron micrograph showing an example of across section of the polymer alloy fiber according to after-mentionedExample 8 of the present invention.

FIG. 10 is a transmission electron micrograph showing an example of alongitudinal section of the polymer alloy fiber according toafter-mentioned Example 8 of the present invention.

FIG. 11 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example8 of the present invention.

FIG. 12 is a transmission electron micrograph showing an example of alongitudinal section of the nanoporous fiber according toafter-mentioned Example 8 of the present invention.

FIG. 13 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 9 of the present invention.

FIG. 14 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example9 of the present invention.

FIG. 15 is a transmission electron micrograph showing an example of alongitudinal section of the nanoporous fiber according toafter-mentioned Example 9 of the present invention.

FIG. 16 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 10 of the present invention.

FIG. 17 is a transmission electron micrograph showing an example of alongitudinal section of the polymer alloy fiber according toafter-mentioned Example 10 of the present invention.

FIG. 18 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example10 of the present invention.

FIG. 19 is a transmission electron micrograph showing an example of alongitudinal section of the nanoporous fiber according toafter-mentioned Example 10 of the present invention.

FIG. 20 is a transmission electron micrograph showing an example of across section of polymer alloy pellets according to after-mentionedComparative Example 2 in the present invention.

FIG. 21 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 15 of the present invention.

FIG. 22 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example15 of the present invention.

FIG. 23 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 16 of the present invention.

FIG. 24 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example16 of the present invention.

FIG. 25 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 19 of the present invention.

FIG. 26 is a transmission electron micrograph showing an example of across section of a nanoporous fiber according to after-mentioned Example19 of the present invention.

FIG. 27 is a transmission electron micrograph showing an example of across section of a polymer alloy fiber according to after-mentionedExample 35 of the present invention.

FIG. 28 is a diagram showing an example of a spinning machine.

FIG. 29 is a diagram showing an example of a false-twist texturingmachine.

FIG. 30 is a diagram showing an example of a spinneret.

FIG. 31 is a diagram showing an example of a spinning machine.

FIG. 32 is a diagram showing an example of a drawing machine.

FIG. 33 is a diagram showing an example of a spinning machine.

FIG. 34 is a diagram showing an example of a draw false-twist texturingmachine.

REFERENCE NUMERALS

-   1: hopper-   2: melting section-   3: spinning pack-   4: spinneret-   5: cooling equipment-   6: line of thread-   7: thread-collecting finishing guide-   8: first take-up roller-   9: second take-up roller-   10: wound yarn-   11: undrawn yarn-   12: feed roller-   13: heater-   14: cooling plate-   15: twister-   16: delivery roller-   17: false-twisted yarn-   18: weighing section-   19: orifice length-   20: orifice diameter-   21: static mixer-   22: undrawn yarn-   23: feed roller-   24: first hot roller-   25: second hot roller-   26: delivery roller (room temperature)-   27: drawn yarn-   28: metering device-   29: blending tank-   30: extrusion-kneader-   31: first hot roller-   32: second hot roller

BEST MODE FOR CARRYING OUT THE INVENTION

The nanoporous fibers according to the present invention will bedescribed below.

Examples of polymers for constituting the nanoporous fibers of thepresent invention are thermoplastic polymers such as polyesters,polyamides and polyolefins; thermosetting polymers such as phenolresins; polymers with poor thermoplasticity, such as polyvinyl alcoholsand polyacrylonitriles; and biopolymers, of which thermoplastic polymersare preferred for their satisfactory moldability.

Among them, most of polyesters and polyamides have a high melting pointand are more preferred. The melting point of the material polymer ispreferably 165° C. or higher for satisfactory thermal stability. Ingeneral, for example, a polylactic acid (hereinafter may be referred toas “PLA”), PET and N6 have melting points of around 170° C., around 255°C. and around 220° C., respectively, and are preferred.

The polymer may further comprise additives such as particles, flameretardants and antistatics. In addition, the polymer may furthercomprise other copolymerized components within ranges not deterioratingthe properties of the polymers. For retaining inherent thermal stabilityand mechanical properties of the polymers, the degree ofcopolymerization is preferably 5% by mole or less, or 5% by weight orless.

For use in, for example, clothing, interior decoration and vehicleinterior decoration, polyesters and polyamides are preferred for theirmelting points, mechanical properties and hands. Among them, nylon 6 andnylon 66 each having a degree of copolymerization of 5% by mole or lessor 5% by weight or less and having a relative viscosity of 2 or more;PETs, polytrimethylene terephthalates and polybutylene terephthalateseach having an intrinsic viscosity of 0.50 or more; and PLAs each havinga weight-average molecular weight of 7×10⁴ or more are specificallypreferred. The content of these polymers in the porous fiber ispreferably 80% by weight or more.

An essential feature of the porous fibers of the present invention isthat the porous fibers have pores each having a diameter of 100 nm orless.

As is mentioned at the outset, the term “porous fiber” used in thepresent invention means a fiber containing pores each having a diameterof 100 nm or less in a number of one or more per square micrometer atcross section of a fiber and is referred to as “nanoporous fiber” in thepresent invention. Such a fiber having nanopores as in the presentinvention can have dramatically increased liquid adsorptivity and/or gasadsorptivity.

Another essential feature is that the area ratio of pores each having adiameter of 200 nm or more to the total cross section of the fiber is1.5% or less. The visible radiation has a wavelength of about 400 to 800nm. Thus, by substantially eliminating coarse pores each having adiameter of 200 nm or more, the nanoporous fiber is prevented fromdecreasing in color property. The diameters and areas of the pores canbe estimated by cutting the nanoporous fiber into ultrathin peaces andobserving the ultrathin peaces under a transmission electron microscope(TEM). These parameters are determined in this manner in the presentinvention.

The pores may have irregular profiles such as oval profiles and do notalways have perfect circular profiles. The diameters of the pores hereinare therefore determined from the areas of the pores, assuming that thepores have perfect circular profiles.

The phrase “total cross section of the fiber” refers to the area of across section of a mono-filament and means a total area of polymersections and pore sections. Such areas can be relatively easilydetermined by using an image processing software such as WINROOF. Thearea ratio of pores each having a diameter of 50 nm or more to the totalcross section of the fiber is preferably 1.5% or less, and morepreferably 0.1% or less in the porous fibers of the present invention.

The pores preferably have an average diameter of 0.1 to 50 nm. Thissubstantially prevents the visible radiation from scattering, and theresulting fiber is optically transparent to the visible radiation butexhibits a new function of blocking harmful ultraviolet rays, since thepores each have a diameter near to the wavelengths of ultraviolet rays.In addition, the resulting fiber has a dramatically increased surfacearea and thereby exhibits high hygroscopicity and/or adsorptivityunexpectable in conventional porous fibers.

Such a multitude of fine pores serve to dramatically-improve thecapability of adsorbing various liquids (fluids) such as organicsolvents in addition to water. However, an excessively small averagediameter of the pores may cause filling of the pores as a result of, forexample, heat treatment. Thus, the present inventors have found that thepores more preferably have an average diameter of 5 to 30 nm.

An example of the nanoporous fibers of the present invention is shown inFIG. 1 as a transmission electron micrograph of a cross section of ananoporous N6 fiber. The figure shows minute shades of gray by metalstaining, in which dark regions are regions at high density of N6, andbright regions are regions at low density of N6. The bright regions areconsidered to correspond to pores. The pores may be connected poresbeing connected with each other or unconnected pores substantiallywithout being connected with each other.

In the present invention, the term “connected pores” refers to poreswhich are connected with each other and substantially extend from asurface top layer to an inner layer of the fiber. The term “unconnectedpores” refers to pores which are not substantially connected with eachother, in which pores in a surface layer of the fiber are substantiallyisolated from pores in an inner layer thereof.

These pores are capable of taking various molecules therein, asmentioned later. For satisfactory washing resistance and sustainedreleasability of such molecules, the pores are preferably unconnectedpores, since such unconnected pores can trap or encapsulate the takenmolecules to some extent.

When the fiber has connected pores, the polymer constituting the fiberhas reduced continuity and may often have a decreased strength. Theporous fiber according to the present invention should essentially havea strength of 1.0 cN/dtex or more when the fiber has connected pores.

Whether the nanopores in the present invention are formed as unconnectedpores or as connected pores can be controlled by appropriately selectingblending and dissolving-off conditions of the islands-part polymer inthe polymer alloy fiber serving as a raw yarn.

The porous fiber having connected pores can have a strength of 1.0cN/dtex or more by controlling the average diameter of the pores to 50nm or less.

As is described above, the nanoporous fibers according to the presentinvention have myriad nanopores and thereby have increased specificsurface areas to show excellent hygroscopicity and/or adsorptivity.

The present inventors have had the following findings. Specifically, theratio of moisture adsorption (ΔMR) of the nanoporous fibers ispreferably 4% or more. The ratio of moisture adsorption (ΔMR) may becontrolled to 4% or more according to, but not limited to, a procedureof forming the nanoporous fibers according to the present inventionusing a hydrophilic polymer inherently having some hygroscopicity.Examples of the hydrophilic polymer are polyamides such as N6 and N66.Even when the nanoporous fibers comprise a not-hydrophilic polymer suchas a polyester, they can have a ratio of moisture adsorption (ΔMR) of 4%or more by incorporating a hygroscopic material into the nanopores.Examples of the hygroscopic material are polyalkylene oxides andmodified products thereof. Such deodorant fibers preferably have anammonia adsorbing rate, for example, of 50% or more, and the porousfibers of the present invention satisfy this requirement. The nanoporousfibers according to the present invention can have an ammonia adsorbingrate of 50% or more according to any suitable procedure, such as byusing a polymer inherently having some odor adsorbing capability toconstitute the nanoporous fibers. Needless to say, any of deodorizersmay be incorporated into the nanopores.

The ammonia adsorbing rate can be determined by the following method.Specifically, 1 g of a fabric comprising 100% of the nanoporous fiber isplaced in a 5-liter Tedlar bag, and 3 liters of a gas containing ammoniais introduced into the bag to adjust the initial concentration (C₀) to40 ppm. The gas is sampled from the Tedlar bag 2 hours later, and theammonia concentration (C₁) is determined. Separately, a blank testwithout using a fabric sample is carried out, and the ammoniaconcentration (C_(B)) is determined 2 hours later. The ammonia adsorbingrate is determined by calculation according to the following equation.

Ammonia adsorbing rate (%)={(C_(B)−C₁)/C_(B)}×100 (%) The porous fibersaccording to the present invention can adsorb not only gases but alsoliquids, may exhibit water retention capability equivalent to cotton tohave a percentage of water retention of 60% or more. The nanoporousfibers according to the present invention can have a percentage of waterretention of 60% or more according to any suitable procedure, forexample, by using a polymer inherently having some water retentioncapability to constitute the nanoporous fibers. Examples of the polymerinherently having some water retention capability are polyamides such asN6 and N66. As a matter of course, a water-absorbing material such as apolyalkylene oxide may be incorporated into the nanopores.

The percentage of water retention can be determined in the followingmanner. Initially, a fabric comprising 100% of the nanoporous fiber isallowed to adsorb water sufficiently by immersing in water for one hour,is hanged on a hanger for one minute, is dewatered in a domestic washingmachine (manufacturer: SANYO, Model: SW150P (A)) for 3 minutes to removeexcess water on the surface of the fiber or in cavities between fibers.

In this procedure, the weight of the fabric sample (W₁) is determined,and, after drying at 60° C. for one hour, the dry weight (W₀) of thesample fabric is determined. Based on these parameters, the percentageof water retention is determined by calculation according to thefollowing equation. In this connection, regular nylons have a percentageof water retention of about 20 to 30%.

Percentage of water retention (%)={(W_(1−W) ₀)/W₀}×100 (%)

Some of the nanoporous fibers of the present invention exhibitreversible liquid-swelling property in a longitudinal direction of theyarn as wool and can exhibit functions as in naturally-occurring fibers,although they are synthetic fibers. The phrase “exhibit reversibleliquid-swelling property” means that, when immersed therein, thenanoporous fiber adsorbs a liquid and swells or elongates in alongitudinal direction of the yarn, and, when the liquid is removedtypically by drying, the nanoporous fiber shrinks in the longitudinaldirection of the yarn to have the original length, and this behavior ofthe fiber is reversibly repeatable. The degree of reversible liquidswelling in a longitudinal direction of the yarn is preferably 6% ormore.

Such nanoporous fibers having reversible liquid-swelling property in alongitudinal direction of the yarn can be produced according to anysuitable procedure, such as by dispersing nanopores homogeneously in antotal cross section of the fiber. The degree of reversible liquidswelling in a longitudinal direction of the yarn can be controlled to 6%or more by rendering the nanopores to have an average diameter 5 of 30nm or less.

The features and advantages mentioned above are essential features andadvantages of the nanoporous fibers according to the present invention.

In addition, the fibers can have functions more easily than conventionalfibers, since the nanopores easily take a variety of functionalmaterials therein.

If a fabric made from a regular polyester fiber, for example, is mixedwith a moisture absorbent containing a polyethylene glycol (hereinaftermay be referred to as “PEG”) having a molecular weight of 1000 or morein order to impart hygroscopicity thereto, the fiber cannotsignificantly take the moisture absorbent therein. In contrast, ananoporous fiber of the present invention comprising PET can take alarge quantity of the moisture absorbent therein, if imparted.

Squalanes are natural-occurring oil components extracted from sharkliver and receive attentions as a substance having skin-care functionsby the action of moisturizing. If a fabric made from a regular polyesterfiber is mixed with such a squalane, the fiber cannot significantly takethe squalane therein. In contrast, a fabric comprising the nanoporousfiber of the present invention can take a large quantity of a squalanetherein and shows significantly improved washing resistance. This issurprising for those familiar with regular polyester fibers.

Examples of functional agents to be taken in are, in addition to suchmoisture absorbents and humectants, flame retardants, water repellents,cold insulators, heat insulators and lubricating agents. Such agents canhave any shape in addition to such a fine-particle shape. The agentsalso include health-beauty promoting agents such as polyphenols, aminoacids, proteins, capsaicin and vitamins; agents for dermatoses such asdermatophytosis; and medicaments such as antiseptics, anti-inflammatoryagents and analgesics. In addition, agents for adsorbing and/ordecomposing harmful substances, such as polyamines and photocatalyticnanoparticles, can also be used. If desired, it is also possible toallow the fiber to take one or more monomers capable of forming anorganic or inorganic polymer therein and to allow them to be polymerizedto form a hybrid material. The fiber can also have selectiveadsorptivity and/or catalytic activity by activating walls of the poresby chemical processing utilizing their large specific surface area. Itis also surprising that the fiber can have any optional function withany optional effect.

The strength of the nanoporous fibers of the present invention ispreferably 1.5 cN/dtex or more for higher tear strength and/ordurability of the resulting fibrous article, and is more preferably 2cN/dtex or more, and further preferably 2.5 cN/dtex or more.

The elongation percentage is preferably 20% or more for higherdurability of the fibrous article.

To control the strength to 1.5 cN/dtex or more and the elongationpercentage to 20% or more, the nanoporous fiber is preferably formed byusing a polymer that can satisfy these requirements even if the polymeralone is made into yarns. For further improving the strength, it isimportant to use a polymer such as a polyamide or polyester which canyield a high strength when the polymer alone is made into yarns, or toreduce the area ratio of coarse pores and to reduce the average diameterof pores. The selection of a higher soluble polymer for use in thepolymer alloy fiber serving as a precursor is also important. The highersoluble polymer preferably does not comprise such a substance as toinhibit the developing of a fiber structure, such as apseudocrosslinking component.

The nanoporous fibers of the present invention may have a variety ofprofiles (cross sections) such as a trefoil, cross or hollow profile.Such nanoporous fibers having a modified profile can be prepared byusing a conventional spinneret for fibers having an irregular profile.

The nanoporous region may spread overall at cross section of the fiberor may be unevenly located, for example, in a surface layer or an innerlayer of the fiber or be located eccentrically.

The “nanoporous region” herein refers to a region containing pores eachhaving a diameter of 100 nm or less in a number of one or more persquare micrometer.

When the inner layer part of the fiber comprises a nanoporous region andthe surface layer part of the fiber comprises a regular polymer, theresulting fiber has improved wear resistance, dimensional stabilityand/or strength.

In contrast, when the surface layer part of the fiber comprises ananoporous region and the inner layer part of the fiber comprises aregular polymer, the fiber has improved dimensional stability and/orstrength.

When the nanoporous region is eccentrically unevenly located, the fiberadsorbs water, swells in a longitudinal direction of the yarn and isfurther highly crimped.

When the nanoporous region is located in an outer area of crimps and thefiber swells as a result of water adsorption, the fiber is furtherhighly crimped to thereby improve stretchability and/or bulkiness.

In contrast, when the nanoporous region is located in an inner area ofcrimps, the crimps elongate as a result of water adsorption, and theyarn elongates as wool. Thus, the entanglement of the fabric structureis loosened, and/or the stitches or weaves are enlarged to therebyimprove air permeability.

When the nanoporous region is eccentrically located at cross section ofa fiber as in the above examples, a fabric capable of breathing as aresult of water adsorption can be provided. When the nanoporous regionis unevenly located as described above, the area ratio of the nanoporousregion is preferably 5 to 95%, more preferably 30 to 80%, and furtherpreferably 40 to 60% of the total cross section of the fiber, foryielding satisfactory advantages of the nanoporous region and those ofthe other region. Such a nanoporous fiber having a located nanoporousregion can be prepared by stopping dissolving off the higher solublecomponent from the polymer alloy fiber in the midway to thereby allowthe higher soluble component to remain in the fiber, or by subjecting apolymer alloy and a regular polymer to multi-component fiber spinning toform a conjugated fiber and dissolving off the higher soluble componentfrom the conjugated fiber.

Some of the nanoporous fibers of the present invention may be easilyfibrillated by physical napping, such as buffing or water punching andare useful as fibrillated fibers or fibrous articles derived therefrom.

The diameter of the fibril can be controlled within a range of 0.001 to5 μm, by selecting, for example, the combination of polymers in thepolymer alloy fiber serving as a precursor, physical properties of thepolymer alloy fiber, shape or configuration of pores in the nanoporousfiber, or napping conditions. Among them, the configuration of the poresare important, and the fiber is increasingly fibrillated with a reducingsize of pores and an increasing number of the pores. This is alsoaffected by the size and proportion of the higher soluble polymerblended in the polymer alloy fiber serving as a precursor. Such afibrillated fiber has not been achieved in fibers having an excessivelyhigh wear resistance, such as polyamides, and is very useful.

The nanoporous fibers of the present invention can be used alone or incombination with one or more regular synthetic fibers, regeneratedfibers or naturally-occurring fibers, for example, by mixing yarns,spinning of mixed cut fibers, mixing of cut fibers, combined weaving orcombined knitting. When used in combination with a synthetic fiberhaving excellent dimensional stability and/or durability, the resultingfabric can have improved dimensional stability, durability and/orchemical resistance. When used in combination with a regenerated fiberor a naturally-occurring fiber, the fabric can have further improvedhygroscopicity, water adsorptivity and/or hands.

When the nanoporous fibers of the present invention are yarns, they maybe flat yarns without crimp, crimped yarns or yarns having any otherconfiguration. The nanoporous fibers are preferably crimped yarns, sincethe resulting fabric can have bulkiness and/or stretchability and can beused in a wider range of applications. They can be formed into variousfibrous articles such as continuous fibers, staples, woven fabrics,knitted fabrics, nonwoven fabrics, felts, synthetic leather andthermally molded articles. The fibers are preferably formed into wovenfabrics or knitted fabrics for use as general clothing or products forinterior. Alternatively, the fibers are preferably formed into nonwovenfabrics for use as functional products such as synthetic leather orfilters, adsorptive materials, wiping cloths and abrasive cloths.

As is described above, the nanoporous fibers according to the presentinvention can yield high-quality dyed fabrics that are substantiallyfree from decrease in color property and exhibit excellenthygroscopicity and/or adsorptivity, as compared with conventional porousfibers.

The nanoporous fibers can thereby provide comfortable clothing such aspanty hoses, tights, underwear, shirts, blousons, pants or trousers, andcoats. In addition, they can also be advantageously used for clothingmaterials such as cups and pads; for interior decoration that cancontrol indoor environments, such as curtains, carpets, mats andfurniture; for livingwares such as wiping cloths; for industrialmaterials such as filters and abrasive cloths; and for vehicle interiorsuch as car seats and ceiling materials.

The nanoporous fibers, if adsorbing any functional molecule, can also beused as most advanced materials typically in the fields of environment,medical and information technology, such as health-cosmetic-relatedgoods, base fabrics for medicaments, and electrodes of fuel cells.

The nanoporous fibers of the present invention can be produced by anysuitable method, such as the following method in which a nanoporousfiber is produced by dissolving off a higher soluble polymer from apolymer alloy fiber comprising a lower soluble polymer and the highersoluble polymer. The method will be described below.

In the following description, a polymer alloy fiber having anislands-in-sea structure and comprising a lower soluble polymer as a seapart and a higher soluble polymer as islands parts is taken as anexample. In this case, the abundance ratio of islands each having adiameter of 200 nm or more, namely the abundance ratio of coarselyaggregated polymer particles is 3% or less in terms of area ratio of thetotal islands. This significantly avoid decrease in color property inthe resulting nanoporous fibers. The islands may have somewhat deformedelliptic shapes and do not always have perfect circular shapes. Thediameters thereof are determined from the areas of the islands in termsof circle. The area of the total islands is a total area of all theislands present at cross section of a fiber and can be estimated basedon the observation of the cross section of the fiber or the polymerblending ratio. The area ratio of islands each having a diameter of 200nm or more is preferably 1% or less. More preferably, the area ratio ofislands each having a diameter of 100 nm or more is 3% or less. The arearatio of islands each having a diameter of 100 nm or less is furtherpreferably 1% or less.

The islands preferably have an average diameter of 1 to 100 nm, sincesuch a polymer alloy fiber can yield, by removing the islands, ananoporous fiber containing pores with smaller sizes than conventionalporous fibers. The resulting nanoporous fiber containing pores withsizes on the order of nanometers is substantially free from scatteringof visible radiation, exhibits markedly improved color property. Inaddition, it can scatter harmful ultraviolet rays and thereby gains anovel function of ultraviolet ray blocking. Furthermore, the fiber has adramatically increased surface area and can thereby exhibit excellenthygroscopicity and/or adsorptivity unexpectable in conventional porousfibers.

The less the average diameter of the islands is, the more advantageousis from the viewpoints of color property and adsorptivity. However, anexcessively small average diameter may cause excessively largeinteractions due to excessively large interfaces between the polymersand may lead to unstable thinning of the fiber in spinning. Accordingly,the average diameter of islands is more preferably from 10 to 50 nm.

The islands preferably have a lined structure. Thus, the islands-partpolymer supports the polymer alloy upon thinning like reinforcingreinforcing bars and thereby stabilizes the thinning in spinning. The“lined structure” herein refers to a structure in which the ratio of thelength to the diameter of the islands in an axial direction of the fiberis 4 or more. In general, the ratio of the length to the diameter of theislands in an axial direction of the fiber often stands at 10 or more,and such islands often become out of a field of view of a TEM.

To obtain such a polymer alloy fiber which is substantially free fromcoarse islands and contains the homogeneously dispersed nano-sizedislands-part polymer, a key factor is the selection of a combination ofpolymers in consideration of affinity for each other and/or of akneading procedure so as to knead the polymers highly, as mentionedlater.

In another production method, an alloy fiber having the followingspecial layered structure can be used instead of the polymer alloyhaving an islands-in-sea structure.

The “special layered structure” herein refers to a structure in whichthe following condition is observed on TEM observation of a crosssection of the fiber.

Specifically, blended different polymers constitute layers and aretangled with each other in the special layered structure (FIG. 8, atransmission electron micrograph of a cross section of the fiber). Thus,the interface between the different polymers is markedly larger thanthat in the islands-in-sea structure (FIGS. 3 and 16, transmissionelectron micrographs of a cross section of the fiber). This structure isa very unique structure in which the compatibility is higher than thatin the islands-in-sea structure but is lower than that in a homogenousstructure such as PET/PBT. However, the layered structure isdistinguished from a modulated structure caused by “spinodaldecomposition”, since the structure does not show a clear periodicity oflayers. The samples for TEM observation herein are dyed with a metal,and dark regions are the lower soluble polymer, and bright regions arethe higher soluble polymer. The structure in question is a layeredstructure and is structurally apparently distinguished from a“sea-and-sea structure” in which islands parts are not clearlyidentified. The sea-and-sea structure is a very unstable structure whichis formed at a blending ratio near to that where sea/islands arereversed in a polymer blend, and the spinning cannot be significantlystably carried out in this region. The average thickness of one layer ofthe higher soluble component in a cross sectional direction of the fibershould be preferably 1 to 100 nm. In the resulting fiber, the differentpolymers are sufficiently homogeneously dispersed with size on the orderof nanometers and can satisfactorily exhibit properties as a blendedpolymer even if a small amount of one polymer is blended. The averagethickness of one layer of the higher soluble component is preferably 1to 50 nm. The layer observed at cross section of a fiber extends as aline in a longitudinal direction of the fiber (FIG. 10, a transmissionelectron micrograph of a longitudinal section of the fiber).

The polymer alloy fiber having the special layered structure showntypically in the figures can be prepared by a combination of specificpolymers and spinning conditions. It can be prepared, for example, bykneading a polyamide (70 to 85% by weight) and a copolymerized PET (15to 30% by weight) copolymerized with 4 to 6% by mole of a sulfonatecomponent in a static mixer (having a number of splits of 100×10⁴ ormore) arranged in a spinning pack, and spinning the kneaded product.

As is described above, the nanoporous fibers of the present inventioncan be prepared by removing a higher soluble polymer from a polymeralloy fiber in which the higher soluble polymer is homogenouslydispersed with size on the order of nanometers in a lower solublepolymer. According to conventional techniques, when a polymer having alow melting point or low softening point is used as the higher solublepolymer, the polymer is dispersed in large diameter, and the resultingfiber cannot satisfactorily pass through processes such as yarntreatment and fabric treatment, in which a high-temperature treatment iscarried out, such as crimping and throwing. Thus, textured yarns orfabrics subjected to crimping or throwing cannot be substantiallyobtained.

The polymer alloy fiber of the present invention comprises a highersoluble polymer homogenously dispersed with size on the order ofnanometers. Thus, even if a polymer having a low melting point or lowsoftening point is used, the polymer alloy fiber can satisfactorily passthrough yarn processing and/or fabric processing in whichhigh-temperature treatment is carried out, and the resulting product hashigher quality.

The polymers in the polymer alloy fiber has only to be two or moredifferent polymers having different solubilities. Where necessary, thenumber of types of the lower soluble polymer and/or the higher solublepolymer can be increased, and one or more compatibilizers can be used.

The higher soluble polymer in the polymer alloy fiber is preferably apolymer easily soluble in an alkaline solution, since an alkalitreatment process generally used as an after-processing process forregular fibers can be used for removing islands to thereby form a porousfiber. This is a great advantage in consideration that, for example,explosion-proof facilities are required when a polymer soluble in anorganic solvent, such as a polystyrene, is used as the higher solublepolymer.

The higher soluble polymer is more preferably a polymer soluble in hotwater, since the islands can be removed in a scoring or degummingprocess of the fiber. Examples of the polymer easily soluble in analkaline solution are polyesters and polycarbonates. Examples of thepolymer soluble in hot water are polyesters copolymerized with a largequantity of hydrophilic groups; alkylene oxides, polyvinyl alcohols, andmodified products of these polymers.

The reduction finish for removing the higher soluble polymer ispreferably carried out at a rate of 20% by weight or more per hour. Thisprevents filling of pores upon reduction at high temperatures andimproves the productivity. The parameter herein is a reduction speed(rate) of reduction finish, and a process time of reduction finish lessthan one hour can be employed.

To allow the nanoporous fibers of the present invention tosatisfactorily exhibit functions of the nanopores while maintaining themechanical properties thereof, the content of the islands-part polymerserving as a higher soluble polymer in the blend is preferably 5 to 60%by weight, more preferably 10 to 30% by weight, and further preferably15 to 25% by weight.

The polymer alloy fiber does not contain coarsely aggregated polymerparticles and thereby undergoes the spinning process more stably thanconventional equivalents, to obtain a fiber with less yarn unevenness.The yarn unevenness can be evaluated by an Uster unevenness (U %). Thepolymer alloy fiber for use in the present invention preferably has a U% of 0.1 to 5%, since the resulting fibrous articles typically for usein apparel, interior decoration and vehicle interior decoration showless dyeing speck and have high quality. The U % is more preferably 0.1to 2%, and further preferably 0.1 to 1.5%. In contrast, a thick-thinyarn having a U % of 3 to 10% can be used for non-linear yarn for use inapparel. The U % can be controlled to a range from 0.1 to 5% byhomogeneously dispersing the islands-part polymer to the order ofnanometers. The U % can further be controlled by optimizingthe-combination of polymers, weighing and feeding the polymersindependently in kneading, and/or optimizing spinning conditions such asthe opening diameter of the spinneret and cooling conditions. Thethick-thin yarn having a U % of 3% to 10% for obtaining a non-linearyarn can be prepared by employing conventional technologies usedtypically in PET.

The polymer alloy fiber preferably has a strength of 2 cN/dtex or more,since the resulting fiber can satisfactorily pass through processes suchas throwing and weaving/knitting process. The strength is morepreferably 2.5 cN/dtex or more, and further preferably 3 cN/dtex ormore.

The strength of the polymer alloy fiber can be controlled to 2 cN/dtexor more by spinning under such conditions that the polymers areprevented from decomposing.

The strength can be controlled to 2.5 cN/dtex or more by optimizing thekneading procedure. A higher strength can be obtained by optimizingpolymer conditions such as the blending ratio of the higher solublepolymer, viscosity/concentration of terminal groups of the polymer, andthe comonomer component and/or optimizing, for example, spinning/drawingconditions and crimping conditions.

The polymer alloy fiber preferably has an elongation percentage of 15 to70%. The resulting fiber can satisfactorily pass through processes suchas throwing and/or weaving/knitting process. The elongation percentageis preferably 70 to 200% for use as a raw yarn for draw false-twisting.The resulting raw yarn can satisfactorily pass through the falsetwisting process. The elongation percentage is preferably about 70 to500% for use as raw yarn for drawing, since the resulting yarn cansatisfactorily pass through the drawing process. The elongationpercentage of the polymer alloy fiber can be generally controlled byadjusting the spinning rate and/or draw ratio.

A conventional fiber that swells as a result of adsorption ofmoisture/water, such as a polyamide fiber, cannot significantly yield a“highly oriented undrawn yarn” having an elongation percentage of about70 to 200%. This is because the fiber swells during spinning/winding,the wound package deforms and the fiber cannot be wound. The polymeralloy fiber mainly comprising such a polymer, however, can yield ahighly oriented undrawn yarn by blending a polymer that does not swellas a result of adsorbing moisture/water, such as a polyester, in anamount of 5% by weight or more.

The polymer alloy fiber is preferably crimped, for increased bulkinessof the resulting fabric made from the nanoporous fiber. In the case of afalse-twisted yarn, the crimp rigidity (CR) as an indication of crimpingproperty is preferably 20% or more. The CR is more preferably 30% ormore, and further preferably 40% or more. In the case of a mechanicallycrimped yarn or an air-jetted yarn, the number of crimp as an indicationof crimping is 5 or more per 25 mm. The polymer alloy fiber can also becrimped by forming into a side-by-side or eccentric core-in-sheathconjugated yarn. In this case, the number of crimp is preferably 10 ormore per 25 mm. The CR can be generally controlled by modifying falsetwisting conditions such as crimping procedure and device, the number ofrevolutions of twister, and temperature of heater. The CR can becontrolled to 20% or more by setting the temperature of the heater at[(the melting point of the polymer) −70] (° C.) or higher. To furtherincrease the CR, increase of the temperature of the heater and/orreduction in blending ratio of the higher soluble polymer blend iseffective.

The number of crimp of a mechanically crimped yarn or air-jetted yarncan be easily controlled to 5 or more per 25 mm by appropriatelyselecting the crimping machine or modifying the conditions such asfeeding rate.

The number of crimp of a side-by-side or eccentric core-in-sheathconjugated yarn can be controlled to 10 or more per 25 mm, for example,by setting the difference in melt viscosity between polymers to beconjugated at 2 times or more, or by setting the difference in thermalshrinkage between polymers upon spinning separately to 5% or more.

The polymer alloy fiber can be prepared, for example, by the followingmethod, but the production method is not specifically limited thereto.

Specifically, a lower soluble polymer and a higher soluble polymer aremelted and kneaded to obtain a polymer alloy comprising the lowersoluble polymer and the higher soluble polymer in which the lowersoluble polymer and/or higher soluble polymer is finely dispersed. Thisis melt spun to obtain the polymer alloy fiber of the present invention.

In this method, the melting and kneading procedure is important. Inother words, the polymers are forcedly kneaded by using anextrusion-kneader or a static mixer to thereby significantly reducecoarsely aggregated polymer particles.

The conventional technique (Japanese Unexamined Patent Publication(Kokai) No. 56-107069) employs chip blending (dry blending), therebyinvites significant unevenness in blending and fails to prevent theislands-part polymer from aggregating.

For forced kneading, a twin-screw extrusion-kneader is preferably usedas the extrusion-kneader, and a static mixer having a number of splitsof 100×10⁴ or more is preferably used as the static mixer in the presentinvention. The polymers to be kneaded are preferably weighed and fedseparately for preventing uneven blending and/or variation in blendingratio with time. In this case, the polymers may be separately fed aspellets or as molten polymers. The two or more different polymers may befed to a bottom portion of the extrusion-kneader. Alternatively, one ofthese components may be fed in the midway of the extrusion-kneader in aside feed manner.

When a twin-screw extrusion-kneader is used as the kneader; it ispreferred that the polymers are highly kneaded while reducing theresidence time of the polymers. The screw comprises a feeding sectionand a kneading section. The length of the kneading section is preferablyset at 20% or more of the effective length of the screw for highlykneading the polymers. The length of the kneading section is preferablyset at 40% or less of the effective length of the screw. This avoidsexcessively high shear stress and shortens the residence time, thuspreventing thermal degradation of the polymers and/or gelation of thepolyamide component. The kneading section is preferably arranged near tothe discharge port of the twin-screw extruder to thereby shorten theresidence time after kneading and to prevent reaggregation of theislands-part polymer. In addition, a screw having a back-flow functionto feed the polymers in a reverse direction may be arranged in theextrusion-kneader, for further higher kneading.

By using a bent-type kneader to aspirate a decomposed gas duringkneading and/or to reduce the moisture in the polymers, the polymers areprevented from hydrolyzing, and the amount of terminal amino groups in apolyamide or terminal carboxylic acid groups in a polyester can bereduced.

Polymer alloy pellets can thus be prepared by using a twin-screwextrusion-kneader. Examples of preferred combinations of polymers fromthe viewpoint of multiplicity of use are:

Combination 1: a polyamide and a polyester; and

Combination 2: a polymer soluble in hot water and a polymer selectedfrom polyamides, polyesters and polyolefins.

The average diameter of dispersed polymer particles in preferredCombination 1 comprising a polyamide and a polyester is preferably 1 to50 nm. The area ratio of coarsely dispersed polymer particles eachhaving a diameter in terms of circle of 100 nm or more is preferably 3%or less of the total dispersed polymer particles in a cross section of apellet. Such pellets hardly yield coarse islands in the resultingpolymer alloy fiber. The amount of terminal amino groups in the polymeralloy pellets is preferably 6×10⁻⁵ molar equivalent or less per gram ofthe polyamide, for better spinnability or reduced yarn unevenness.

In preferred Combination 2 comprising a polymer soluble in hot water anda polymer selected from polyamides, polyesters and polyolefins, theblending ratio of the polymer soluble in hot water serving as a highersoluble component is preferably 10 to 30% by weight. Thus, an extrudedgut derived from the pellets is satisfactorily spun and cut, whereas theresulting nanoporous fiber exhibits satisfactory functions. The b* valueas an indicator of coloring of the polymer alloy pellets is preferably10 or less, since the resulting fiber can have homogenous hue. Such apolymer soluble in hot water generally has poor thermal stability and issusceptible to coloring due to its molecular structure. However, thecoloring can be prevented by shortening the residence time. Examples ofthe polymer soluble in hot water are polyesters copolymerized with alarge quantity of hydrophilic groups, polyalkylene oxides, polyvinylalcohols, and modified products of these polymers. Among them,polyetheresters, a kind of polyalkylene oxide modified products, arepreferred for their dissolution rate and thermal stability.

The kneader may be arranged separately from a spinning machine, in whichpolymer alloy pellets produced in the kneader is fed to the spinningmachine. Alternatively, the kneader is directly connected to a spinningmachine, in which kneaded and molten polymers are directly spun. When astatic mixer is used as the kneader, it may be placed in a spinningpack.

The chip blending (dry blending) can be carried out in the followingmanner for reducing cost in spinning.

Initially, polymer pellets to be blended are independently weighed andfed to a blending tank and are chip-blended therein. The blending tankpreferably has a capacity of 5 to 20 kg for efficient blending whileavoiding uneven blending. The blended pellets are fed from the blendingtank to an extrusion-kneader, to obtain a molten polymer. The kneadingmay be carried out by using a twin-screw extrusion-kneader or by feedingthe molten polymer into a static mixer arranged in a piping or a pack.Master pellets containing a larger amount of the higher soluble polymercan be used.

The master pellets in polymer alloy pellets comprising a polyamide and apolyester preferably have the following parameters. Specifically, thepolyester is preferably copolymerized with 1.5 to 15% by mole of asulfonate for better affinity for the polyamide. The blending ratiothereof is preferably 30 to 90% by weight for further efficient dilutionof the master pellets. The average weight of the pellets is preferably 2to 15 mg for matching the weight of the virgin polyamide and reducinguneven blending.

The average weight and shape of the pellets are preferably near to thoseof polymer pellets to be diluted, for preventing uneven blending. Morespecifically, the difference in average weight between the polymer alloypellets and the polymer pellets to be diluted is preferably within arange from −20% to +20%.

The residence time from formation and melting of the polymer alloy todischarge from a spinneret is a key factor for inhibiting reaggregationof the islands-part polymer in spinning to thereby reduce coarselyaggregated polymer particles. Thus, the residence time for the polymeralloy from the tip of a melting section to the spinneret is preferablyset within 30 minutes. This requirement must be met particularly in thecase of an alloy comprising a nylon and a PET copolymerized withhydrophilic groups, since the PET copolymerized with hydrophilic groupsis susceptible to reaggregation.

The combination of polymers is an important factor to disperse theislands-part polymer to the order of nanometers. Specifically, acombination of a lower soluble polymer and a higher soluble polymer witha higher affinity allows the higher soluble polymer to disperse asnano-sized islands more easily. For example, when a nylon and apolyethylene terephthalate (PET) are used as the lower soluble polymerand the higher soluble polymer, respectively, the PET is preferably aPET copolymerized with hydrophilic groups copolymerized with asulfonate, a hydrophilic component, such as 5-sodiosulfoisophthalic acid(SSIA) for better affinity for the nylon. In particular, a hydrophilizedPET having a degree of copolymerization with SSIA of 4% by mole or moreis preferred.

The ratio in melt viscosity of the sea-part polymer to the islands-partpolymer is also an important factor. Specifically, the islands-partpolymer tends to disperse on the order of nanometers more easily due toan increasing shear force with an increasing ratio in melt viscosity ofthe sea-part polymer to the islands-part polymer. However, anexcessively large ratio in viscosity may cause uneven kneading and/ordeteriorated spinnability. The viscosity ratio is preferably from about1/10 to 2. In the combination of a polyester or polyester with a polymersoluble in hot water, the viscosity ratio is considered to play a moreimportant role than the affinity between the polymers and is preferablyset at 0.5 to 1.5.

Preferred embodiments of the method for melt-spinning a polymer alloyfiber according to the present invention are as follows.

In a method for melt-spinning a polymer alloy fiber, comprising thesteps of weighing and feeding a lower soluble polymer and a highersoluble polymer independently to a twin-screw extrusion-kneader, meltingand blending the polymers in the twin-screw extrusion-kneader to form apolymer alloy, and melt-spinning the polymer alloy, the step of spinningis preferably carried out so as to satisfy the following conditions (1)to (3):

-   -   (1) the content of the higher soluble polymer in the polymer        alloy is 5 to 60% by weight;    -   (2) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2; and    -   (3) the length of a kneading section of the twin-screw        extrusion-kneader is 20% to 40% of the effective length of the        screws.

Alternatively, in a method for melt-spinning a polymer alloy fiber,comprising the steps of weighing and feeding a lower soluble polymer anda higher soluble polymer independently to a static mixer having a numberof splits of 100×10⁴ or more, melting and blending the polymers in thestatic mixer to form a polymer alloy, and melt-spinning the polymeralloy, the step of spinning is preferably carried out so as to satisfythe following conditions (4) and (5):

-   -   (4) the content of the higher soluble polymer in the polymer        alloy is 5 to 60% by weight; and    -   (5) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2.

Further alternatively, in a method for melt-spinning a polymer alloyfiber, comprising storing and dry-blending two or more different pelletscomprising a lower soluble polymer and a higher soluble polymer,respectively, in a blending tank before melting of the pellets, feedingthe dry-blended pellets to a melting section, and blending andmelt-spinning the dry-blended pellets, the step of spinning ispreferably carried out so as to satisfy the following conditions (6) to(8):

-   -   (6) the content of the higher soluble polymer in the fiber is 5        to 60% by weight;    -   (7) the ratio in melt viscosity of the lower soluble polymer to        the higher soluble polymer is 0.1 to 2; and    -   (8) the blending tank can contain 5 to 20 kg of pellets.

Namely, it is important to set the blending ratio of the higher solublepolymer at 10 to 30% by weight and to set the melt viscosity ratio ofthe lower soluble polymer to the higher soluble polymer in a range from0.1 to 2. In addition, important factors are to set the length of akneading section in a twin-screw extrusion-kneader, if used, at 20 to40% of the effective length of the screws in melt-blending andmelt-spinning using such a twin-screw extrusion-kneader, or to use astatic mixer having a number of splits of 100× or more in melt-blendingand melt-spinning using such a static mixer, or to use a blending tankfor pellets having a capacity of 5 to 20 kg in dry blending andmelt-spinning. The dry blending is inferior in blending uniformity butsuperior in cost to the melt-blending, since the former comprises asimpler process. In the case of dry blending, the above-mentioned masterpellets are preferably used to prevent uneven blending to some extent.

The production methods according to the present invention have theabove-mentioned features, thereby prevent the formation of coarselyaggregated polymer particles, keep good balance in viscoelasticity ofthe polymer alloy, achieve stable spinning and discharging,significantly improve stringiness or spinnability and markedly reduceyarn unevenness, as compared with conventional equivalents.

For higher spinning stability, the polymers preferably have lowconcentrations of terminal groups. In the case of polyamides, the amountof terminal amino groups is preferably 5.5×10⁻⁵ molar equivalent or lessper gram. Such polyamides have less thermal stability than polyestersand are susceptible to gelation as a result of thermal degradation. Inaddition, the present inventors have found in the investigations for thepresent invention that a polymer alloy comprising a polyamide and apolyester is further more susceptible to gelation than a polyamidealone. This is probably because the molecular chain terminal of thepolyester plays a catalytic role. Such a gelated polyamide invites yarnbreaking and/or yarn unevenness, leads to increased process pressuressuch as filtration pressure of the polymer and back pressure of thespinneret to thereby lower the upper limit of the discharge rate orshorten the pack life. The productivity per unit time is markedlydecreased and yarn breaking frequently occurs. Accordingly, such apolyamide/polyester alloy must be avoided from gelation. Thus, theamount of terminal amino groups should preferably be 5.5×10⁻⁵ molarequivalent or less per gram by, for example, blocking the amineterminals of the polyamide to be used in the polymer alloy typicallywith acetic acid. When the polyamide/polyester alloy is once pelletized,the amount of terminal amino groups is preferably set at 6×10⁻⁵ molarequivalent or less per gram of the weight of the polyamide in thepolymer alloy pellets.

The spinning is preferably carried out at temperatures of 300° C. orlower for preventing thermal decomposition and gelation of the polymers.

The spinneret preferably has a diameter larger than regular one. Thisreduces the shear stress on the polymer alloy in a spinneret nozzle tokeep well-balanced viscoelasticity to thereby improve the spinningstability. More specifically, the spinneret is preferably so configuredas to discharge the polymer alloy at a linear velocity of 15 m or lessper minute. In addition, cooling of the line of thread is alsoimportant. The distance from the spinneret to a position at whichpositive cooling starts is preferably set at 1 to 15 cm. Thus, thepolymer alloy that tends to be unstable in elongational flow is rapidlysolidified to thereby stabilize the spinning.

The spinning draft is preferably set at 100 or more for further finelydispersing the islands-part polymer. The spinning rate is preferably setat 800 meters or more per minute for reducing yarn unevenness duringspinning of the undrawn yarn. The spinning rate is more preferably setat 2500 meters or more per minute to thereby develop the fiberstructure, for reducing change in dimensions and physical properties ofthe yarn with time.

The prepared polymer alloy fiber may be subjected to draw thermaltreatment or draw false twisting after being wound or may be directlysubjected to drawing or air-jetting without being wound.

The thermal treatment temperature in crimping is preferably set lowerthan [(the melting point of the lower soluble polymer) −50° C.] forpreventing fusion in the crimping process and improving the quality ofcrimps. The fiber may be converted into short staples and then convertedinto a nonwoven fabric or a spun yarn.

The resulting yarn can be subjected to yarn mixing such as air yarnmixing or combined false-twisting, to mixing and twisting with anotheryarn, or to mixing of cut fibers or spinning of mixed cut fibers. Thepolymer alloy fiber alone or in combination with another yarn can beformed into a woven or knitted fabric or a nonwoven fabric or can beformed into a nonwoven fabric by spun bond or melt blow.

A fabric at least partially comprising a nanoporous fiber can beobtained by dissolving off the higher soluble polymer from the resultingfabric at least partially comprising the polymer alloy fiber.

The fabric can be naturally used as a fabric at least partiallycomprising the polymer alloy fiber without dissolving off the highersoluble polymer. In particular, a highly oriented undrawn yarn can beprepared from a polyamide as described above, which cannot be achievedby conventional equivalents. Thus, a fabric comprising a crimped yarn ora combined filament yarn, such as a combined false twisted yarn,prepared by utilizing this highly oriented undrawn yarn has an excellenthands with further more bulkiness and softness than conventionalequivalents and is of high value even used as intact. Some fabricscomprising 100% of the polymer alloy fiber, other than a combinedfilament yarn, may exhibit improved thermal stability and/or mechanicalproperties by the action of the nanosized polymer alloy and are of highvalue as intact.

If a fabric comprising 100% of the nanoporous fiber has insufficientdimensional stability and/or wear resistance, these requirements may besatisfied by using another yarn in combination, as mentioned above. Inthis case, the polymer alloy fiber serving as a precursor of thenanoporous fiber is subjected to reduction finish preferably at a rateof 20% by weight or more per hour on the weight basis of the polymeralloy in dissolution off of the higher soluble polymer.

As is described above, the nanoporous fibers of the present inventioncan be prepared by using the polymer alloy fiber which is prepared by amethod unlike conventional equivalents. They have pores with lessdimensions than conventional equivalents, are substantially free fromcoarse pores, can yield excellent materials usable in clothing and othervarious fields and are epoch-making.

EXAMPLES

The present invention will now be described in detail by way of thefollowing examples. The physical properties in the examples weredetermined by the following methods.

A. Melt Viscosity of Polymer:

The melt viscosity of a sample polymer was determined using Capillograph1B available from Toyo Seiki Seisaku-Sho, Ltd. The residence time of thesample polymer from charging of the sample to the beginning ofdetermination was set at 10 minutes.

B. Relative Viscosity of Nylon:

Sample nylon pellets were dissolved in a 98% sulfuric acid solution to aconcentration of 0.01 mg/ml, and the relative viscosity was determinedat 25° C.

C. Intrinsic Viscosity [η] of Polyester:

The intrinsic viscosity was determined in o-chlorophenol at 25° C.

D. Melting Point:

The melting point was defined as the peak top temperature at which asample polymer melted in a second run as determined using Perkin ElmaerDSC-7 at a temperature elevation rate of 16° C. per minute ad an amountof the sample of 10 mg.

E. Mechanical Properties:

A load-elongation curve was determined at room temperature (25° C.) anda tension speed of 100% per minute under conditions shown in JapaneseIndustrial Standards (JIS) L1013. In this procedure, the strength wasdefined by dividing the load at break by the initial fineness, and theelongation was defied by dividing elongation at break by the initiallength of the sample. From these parameters, a strength elongationpercentage curve was determined.

F. Uster Unevenness (U %) of Polymer Alloy Fiber:

The Uster unevenness was determined using USTER TESTER 4 available fromZellweger Uster in a normal mode at a yarn feed speed of 200 m perminute.

G. Thermal Shrinkage:

-   -   Thermal shrinkage (%)=[(L0−L1)/L0)]×100 (%)    -   L0: The original length of a skein wound from drawn yarn as        determined at an initial tension of 0.09 cN/dtex    -   L1: The length of the skein at an initial tension of 0.09        cN/dtex after determination of L0, treatment in boiled water for        fifteen minutes under substantially no load and air-drying.

H. TEM Observation of Cross Section of Fiber:

Ultrathin peaces of a sample fiber in a cross-sectional direction or alongitudinal sectional direction were prepared, and the cross sectionsof the fiber were observed using a transmission electron microscope(TEM). Where necessary, the sections were subjected to metal staining.

TEM device: Model H-7100FA available from Hitachi Ltd.

I. Diameters of Pores or Island-component Polymer:

The diameter of pores was determined in the following manner. Thediameters of islands in terms of circle were determined from TEMphotographs of the cross section of the fiber using an image processingsoftware (WINROOF). If the shapes of the islands were excessively fineor complicated and the analyses thereof by WINROOF was difficult, theshapes were analyzed by visual observation manually. The averagediameter was determined as a simple number-average of the determineddiameters.

The average diameter was determined by using 300 or more pores selectedat random in one cross section. The diameter determination was carriedout carefully in consideration of the condition of the sample, becausesuch ultrathin samples for TEM observation often cause breakage.Inorganic fine particles and voids therearound were not included in thepores. The diameter of the islands-part polymer was determined inaccordance with the determination of the diameters of the pores.

J. Evaluation of Color Property:

A prepared sample was dyed according to a conventional procedure, andthe color property was compared with that of a comparative sample dyedunder the same conditions. The comparative sample was prepared byspinning polymers constituting a nanoporous fiber according to aconventional procedure in the following manner.

In the case of a nylon, a sample fibrous article was dyed with a stainsolution containing a dye “Nylosan Blue N-GFL” available from ClariantJapan Co., Ltd. at pH 5 in a concentration of 0.8% by weight of thefibrous article at a liquor-goods ratio of 100 at 90° C. for 40 minutes.

In the case of a polyester, a sample fibrous article was dyed with astain solution containing a dye “Foron Navy S-2GL” available fromClariant Japan Co., Ltd. at pH 5 in a concentration of 0.8% by weight ofthe fibrous article at a liquor-goods ratio of 100 at 130° C. (110° C.in the case of polylactic acid) for 40 minutes.

The color property of the sample was determined according to thefollowing four criteria. “Excellent” and “Good” were passed the test,and “Fair” and “Failure” were not passed the test.

-   -   Excellent: almost equal to or high than that of the comparative        sample    -   Good: somewhat lower than that of the comparative sample but        enough for use in clothing    -   Fair: somewhat lower than that of the comparative sample    -   Failure: significantly lower than that of the comparative sample

K. Ratio of Moisture Adsorption (ΔMR):

About 1 to 2 g of a sample was weighed in a weighing bottle, dried at110° C. for 2 hours, and the weight of the dried sample (W0) wasdetermined. Next, the sample substance was held to 20° C. at relativehumidity of 65% for 24 hours, whose weight was then determined (W65),and the sample substance was then held to 30° C. at relative humidity of90% for 24 hours, whose weight was then determined (W90). The ratio ofmoisture adsorption (ΔMR) was determined by calculation according to thefollowing equations.MR65=[(W65−W0)/W0]×100%   (1)MR90=[(W90−W0)/W0]×100%   (2)ΔMR=MR90−MR65   (3)

L. Reversible Water Swelling and Percentage of Swelling in LongitudinalDirection of Yarn:

The original length (L0′) of a sample fiber was determined after dryingthe fiber at 60° C. for 4 hours. The fiber was immersed in water at 25°C. for 10 minutes and was taken out, and the length of the fiber aftertreatment (L1′) was determined immediately thereafter. The length of thefiber after drying (L2′) was then determined after drying the fiber at60° C. for 4 hours.

The procedure of drying and immersion in water was repeated a total ofthree times. The sample was evaluated to have reversible water swellingwhen it showed a percentage of swelling in a longitudinal direction ofthe yarn in the third procedure of 50% or more of that in the firstprocedure. The percentage of swelling in a longitudinal direction of theyarn was determined by calculation according to the following equation.The length of the fiber was determined by binding the sample fiber withtwo colored yarns at an interval of about 100 mm, and measuring thelength between the two yarns.

Percentage of swelling (%) in longitudinal direction of theyarn=((L1′−L0′)/L0′)×100 (%)

M. Percentage of Water Retention:

The percentage of water retention was determined in the followingmanner. Initially, a sample was allowed to adsorb water sufficiently byimmersing in water at 25° C. for one hour, hanged on a hanger for oneminute, and dewatered in a domestic washing machine for 3 minutes toremove excess water on the surface of the fiber or in cavities betweenfibers. In this procedure, the weight of the fabric sample (W₁) wasdetermined, and, after drying at 60° C. for one hour, the dry weight(W₀) of the sample fabric was determined.

Percentage of water retention (%)={(W₁−W₀)/W₀}100 (%)

N. Ammonia Adsorbing Rate

1 g of a sample fabric comprising 100% of a nanoporous fiber was placedin a 5-liter Tedlar bag, and 3 liters of a gas containing ammonia wasintroduced into the bag to adjust the initial concentration (C₀) at 40ppm. The gas was sampled from the Tedlar bag 2 hours later, and theammonia concentration (C₁) was determined. Separately, a blank testwithout using a fabric sample is carried out, and the ammoniaconcentration 2 hours later (C_(B)) was determined. The ammoniaadsorbing rate was determined by calculation according to the followingequation.

Ammonia adsorbing rate (%)={(C_(B)−C₁)/C_(B)}×100 (%)

O. Crimping Property CR of False-twisted Yarn:

A sample false-twisted yarn was wound, treated in boiling water for 15minutes under substantially no load and air-dried for 24 hours. Thesample was immersed in water under a load of 0.088 cN/dtex (0.1 gf/d),and the length of the skein 2 minutes later (L0″) was determined. Thenthe load of 0.088 cN/dtex was replaced with a slight load of 0.0018cN/dtex (2 mgf/d) in water, and the length of the skein 2 minutes later(L1″) was determined. CR was determined by calculation according to thefollowing equation.CR(%)=[(L0″L1″)/L0″]×100 (%)

P. Number of Crimps:

A sample fiber 50 mm long was sampled, the number of crimp (peaks) per25 mm was determined, and the number of crimp was defined as the half ofthe above-determined value.

Q. Color Tone (b*):

The color tone b* was determined using a MINOLTA SPECTROPHOTOMETERCM-3700d with a light source of D65 (color temperature of 6504K) in avisual field of 10 degrees.

Example 1

A N6 (80% by weight) and a copolymerized PET (20% by weight) were meltedand kneaded in a twin-screw extrusion-kneader at 260° C. to obtainpolymer alloy pellets. The N6 had a relative viscosity of 2.15, a meltviscosity of 274 poises (280° C. at a rate of shear of 2432 sec⁻¹), amelting point of 220° C., and an amount of terminal amino groups of5.0×10⁻⁵ molar equivalent per gram as a result of blocking amineterminals with acetic acid. The copolymerized PET had an intrinsicviscosity of 0.60, a melt viscosity of 1400 poises (280° C. at a rate ofshear of 2432 sec⁻¹) and a melting point of 250° C., had beencopolymerized with 5% by mole of 5-sodiosulfoisophthalic acid andcontained 0.05% by weight of titanium oxide.

The transmission electron micrograph of a cross section of the polymeralloy pellets is shown in FIG. 5. The copolymerized PET as islands haddiameters in terms of circle of 20 to 30 nm (average diameter ofdispersed particles of 26 nm) and were substantially free from coarseislands each having a diameter in terms of circle of 100 nm or more.Thus, the copolymerized PET was homogeneously dispersed with size on theorder of nanometers in N6.

The average weight of the pellets was 3 mg, and the amount of terminalamino groups is 3.3×10⁻⁵ molar equivalent per gram of the weight of N6.The kneading conditions are as follows.

Screw type: one-direction fully interlocking double shred

Screw: diameter of 37 mm, effective length of 1670 mm, L/D=45.1

-   -   The length of the kneading section was 28% of the effective        length of the screw.    -   The kneading section was arranged on the discharge side from        one-thirds of the effective length of the screw.    -   Having three back flow sections in the midway

Feed of polymer: N6 and the copolymerized PET were independently weighedand were separately fed to the kneader.

Temperature: 260° C.

Vent: 2 points

The polymer alloy was melted in a melting section 2 at 270° C. andintroduced to a spin block at a spinning temperature of 275° C. Themolten polymer alloy was filtrated through a metallic nonwoven fabrichaving a diameter of ultrafiltration of 15 μm and subjected to meltspinning (FIG. 28). The residence time from the melting section 2 todischarge was 10 minutes. In this procedure, a spinneret having anorifice diameter of 0.3 mm and an orifice length of 0.65 mm was used, ata discharge rate per orifice of 2.1 g per minute and a linear velocityof the discharged polymer alloy in the spinneret of 28 meters perminute. The distance between the lower end of the spinneret to the startpoint of cooling (upper end of a cooling equipment 5) was 9 cm. Thedischarged thread was cooled and solidified by a cooling air at 20° C.over one meter, fed with an oil by an finishing guide 7 arranged 1.8meter down the spinneret 4 and wound through a first take-up roller 8and a second take-up roller 9 not heated at a rate of 3800 meters perminute.

In this procedure, the fiber showed good spinnability and was free from,for example, Barus phenomenon in which the discharged polymer swellsdirectly below the spinneret, or end breakage due to insufficientstringiness or spinnability. The fiber invited no yarn breaking duringcontinuous spinning for 24 hours. The yarn did not cause deformation ofthe wound package due to swelling with time, which constitutes a problemin regular nylon yarns, and showed good handleability.

The undrawn polymer alloy yarn had satisfactory physical properties suchas a strength of 2.6 cN/dtex, an elongation percentage of 138% and a U %of 0.9%. This undrawn yarn was subjected to draw false-twisting using adevice shown in FIG. 29, to obtain a false-twisted polymer alloy yarnwith false-twisting directions of S and Z. This procedure was carriedout at a draw ratio of 1.5, a temperature of a heater 13 of 165° C.,using a friction type false twisting machine withthree-axes-urethane-disk as a twister 15. The ratio of the surfacevelocity of rotated disks to the speed of texturing (D/Y ratio) was setat 1.65. The yarn was satisfactorily processed without end breakage andwinding around the roller and twister.

The resulting 87 dtex, 24-filament false-twisted yarn had excellentphysical properties,including a strength of 2.7 cN/dtex, an elongationpercentage of 21%, a thermal shrinkage of 8%, a U % of 1.0% and a CR of38% (Table 2) and showed good crimping quality without not-untwistedportions.

The cross section of a mono-filament of the resulting crimped polymeralloy yarn was observed under a TEM and was found to have anislands-in-sea structure comprising N6 as a sea (dark region) and thecopolymerized PET as islands (bright region) (FIG. 3) with an averagediameter of the islands of 25 nm. Thus, a polymer alloy fiber comprisingthe copolymerized PET homogeneously dispersed with size on the order ofnanometers was prepared.

The area ratio of islands each having a diameter of 200 nm or more tothe total islands was 0.1% or less, and the area ratio of islands eachhaving a diameter of 100 nm or more was 0.9%. The “area ratio to thetotal islands” refers to the area ratio to the total area of the islandsparts and serves as an indicator of coarse polymer aggregates. The TEMobservation of the longitudinal section of the fiber shows that theislands constitute a lined structure (FIG. 4). The transmission electronmicrograph of a cross section of the melt-kneaded polymer alloy chip isshown in FIG. 5, showing that the islands-part polymer is ultrafinelydispersed with a particle diameter of 20 to 30 nm, being equivalent tothe diameter of the islands-part polymer at cross section of a fiber(FIG. 3). The polymer was elongated by a factor of about 200 times fromdischarge from the spinneret through draw false-twisting. Thus, thediameter of the islands-part polymer of the fiber in a cross sectionshould be one-fourteenths or less that in the material polymer alloy.However, the diameter of the islands-part polymer at cross section of afiber is substantially equal to that in the material chip. Thisindicates that the islands-part polymer reaggregated between melting ofthe polymer alloy and discharging from the spinneret. To allow theislands-part polymer to disperse homogeneously with size on the order ofnanometers while preventing the reaggregation, the spinning conditionsshould be essentially chosen appropriately, as in the present example.

The false-twisted polymer alloy yarns with false-twisting directions ofS and Z were aligned and knitted into a round braid of 20 G. The roundbraid was treated with a 3% by weight aqueous sodium hydroxide solution(95° C., liquor ratio of 1:50) for one hour to dissolve off 99% or moreof the copolymerized PET from the false-twisted polymer alloy yarn tothereby obtain a fibrous article comprising a nanoporous N6 fiber andhaving a bulkiness of 63 cm³/g.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property without dyeing speck. Thisarticle had a ratio of moisture adsorption (ΔMR) of 5.6% and exhibitedmuch higher hygroscopicity than cotton.

The side of the nanoporous N6 fiber sampled from the round braid wasobserved under a SEM to find that the fiber had a smooth surface withoutunevenness at a magnification of about 2000 times. The cross section ofthe nanoporous N6 fiber was observed under a TEM (FIG. 1) to find poreseach having a diameter of about 20 to 30 nm. The pores had an average of25 nm and were substantially free from coarse pores each having adiameter of 50 nm or more.

This fiber had unconnected pores as shown in FIG. 1 and had a strengthof 2.0 cN/dtex and an elongation percentage of 25%, showing that thefiber had sufficient mechanical properties as a fibrous article. Thisexhibited reversible water swelling, and the yarn sampled from the roundbraid comprising the nanoporous N6 fiber after setting at 180° C. forone minute had a percentage of swelling in a longitudinal direction ofthe yarn of 7.3%. The physical properties of the nanoporous N6 fiber areshown in Table 1.

Example 2

The N6 and the copolymerized PET were subjected to melt-kneading by theprocedure of Example 1, except for blending 95% by weight of N6 and 5%by weight of the copolymerized PET. The kneaded product was subjected tomelt spinning and draw false-twisting by the procedure of Example 1,except for changing the discharge rate per one orifice and the number ofspinneret orifices, to obtain a 90 dtex, 34-filament crimped polymeralloy yarn. The yarn could be satisfactorily spun without any yarnbreaking during continuous spinning for 24 hours.

The resulting highly oriented undrawn yarn had excellent propertiesincluding a strength of 2.7 cN/dtex and a U % of 0.8%. The yarn showedgood processability without any yarn breaking in the draw false-twistingprocess. The crimped yarn had a high bulkiness in terms of a CR of 45%and exhibited excellent crimping quality with satisfactory untwisting.The cross section of the resulting crimped polymer alloy yarn wasobserved under a TEM and was found to have an islands-in-sea structure.The resulting polymer alloy fiber comprises the copolymerized PEThomogeneously dispersed with size on the order of nanometers. Theislands had an average diameter of 20 nm. The area ratio of islands eachhaving a diameter of 200 nm or more to the total islands was 0.1% orless, and the area ratio of islands each having a diameter of 100 nm ormore was 1% or less. The observation of a cross section of the fibershows that the islands-part polymer has a lined structure. The physicalproperties of the false-twisted yarn are shown in Table 2.

The crimped polymer alloy yarn was subjected to soft-twisting of 300T/m, and a plain woven fabric was formed by using the soft-twisted yarnas a warp and a weft, from which 99% or more of the copolymerized PETwas removed by an alkali treatment by the procedure of Example 1, tothereby obtain a woven fabric comprising a nanoporous N6 fiber.

The woven fabric comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property without dyeing speck. The crosssection of the nanoporous N6 fiber sampled from the woven fabric wasobserved under a TEM, to find that holes from which the islands-partpolymer was removed constitute unconnected pores having an averagediameter of 25 nm without coarse pores having a diameter of 50 nm ormore. The nanoporous N6 fiber has excellent physical properties as shownin Table 1.

Example 3

The N6 and the copolymerized PET were subjected to melt-kneading by theprocedure of Example 1, except for blending 90% by weight of N6 and 10%by weight of the copolymerized PET. The kneaded product was subjected tomelt spinning and draw false-twisting by the procedure of Example 1,except for changing the discharge rate per one orifice and the number ofspinneret orifices, to obtain a 90 dtex, 34-filament crimped polymeralloy yarn. The yarn could be satisfactorily spun without any yarnbreaking during continuous spinning for 24 hours. The resulting highlyoriented undrawn yarn showed excellent properties including a strengthof 2.7 cN/dtex and a U % of 0.8%. The yarn showed good processabilitywithout any yarn breaking in the draw false-twisting process. Thecrimped yarn had a high bulkiness in terms of a CR of 40% and exhibitedexcellent crimping quality with satisfactory untwisting.

The cross section of the crimped polymer alloy yarn was observed under aTEM and was found to have an islands-in-sea structure. The islands hadan average diameter of 25 nm, showing that the polymer alloy fibercomprises the copolymerized PET homogeneously dispersed with size on theorder of nanometers. The area ratio of islands each having a diameter of200 nm or more to the total islands was 0.1% or less, and the area ratioof islands each having a diameter of 100 nm or more was 1% or less. Theobservation of a cross section of the fiber shows that the islands-partpolymer has a lined structure. The physical properties of thefalse-twisted yarn are shown in Table 2.

The crimped polymer alloy yarn was subjected to soft-twisting of 300T/m, and a plain woven fabric was formed by using the soft-twisted yarnas a warp and a weft, from which 99% or more of the copolymerized PETwas removed by an alkali treatment by the procedure of Example 1, tothereby obtain a woven fabric comprising a nanoporous N6 fiber. Thewoven fabric comprising the nanoporous N6 fiber was dyed and was foundto have excellent color property without dyeing speck. The cross sectionof the nanoporous N6 fiber sampled from the woven fabric was observedunder a TEM, to find that holes from which the islands-part polymer wasdissolved off constitute unconnected pores having a diameter of 20 nm orless without coarse pores having a diameter of 50 nm or more. Thenanoporous N6 fiber has excellent physical properties as shown in Table1

Example 4

The N6 and the copolymerized PET were subjected to melt-kneading by theprocedure of Example 1, except for blending 50% by weight of N6 and 50%by weight of the copolymerized PET. The kneaded product was subjected tomelt spinning and draw false-twisting by the procedure of Example 1,except for changing the discharge rate per one orifice and the number ofspinneret orifices, to obtain a 150 dtex, 34-filament crimped polymeralloy yarn. The yarn could be satisfactorily spun without any yarnbreaking during continuous spinning for 24 hours.

The resulting highly oriented undrawn yarn showed excellent propertiesof a strength of 2.5 cN/dtex and a U % of 1.0%. The yarn showed goodprocessability without any yarn breaking in the draw false-twistingprocess. The crimped yarn exhibited excellent crimping quality withsatisfactory untwisting. A transmission electron micrograph of a crosssection of the crimped polymer alloy yarn is shown in FIG. 6, showingthat the copolymerized PET constitutes beaded islands each having adiameter of 10 to 20 nm and is free from coarsely aggregated polymerparticles. The area ratio of islands each having a diameter of 200 nm ormore to the total islands was 0.1% or less, and the area ratio ofislands each having a diameter of 100 nm or more was 1% or less. Theobservation of a cross section of the fiber shows that the islands-partpolymer has a lined structure. The physical properties of thefalse-twisted yarn are shown in Table 2.

The crimped polymer alloy yarn was subjected to soft-twisting of 300T/m, and a plain woven fabric was formed by using the soft-twisted yarnas a warp and a weft, from which 99% or more of the copolymerized PETwas removed by an alkali treatment by the procedure of Example 1, tothereby obtain a woven fabric comprising a nanoporous N6 fiber. Thewoven fabric comprising the nanoporous N6 fiber was dyed and was foundto have excellent color property without dyeing speck. The cross sectionof the nanoporous N6 fiber sampled from the woven fabric was observedunder a TEM, to find that holes from which the islands-part polymer wasdissolved off constitute unconnected pores having an average diameter of25 nm without coarse pores having a diameter of 50 nm or more (FIG. 7).The nanoporous N6 fiber has excellent physical properties as shown inTable 1.

Example 5

The N6 and the copolymerized PET were subjected to melt kneading, meltspinning and draw false-twisting by the procedure of Example 1, exceptfor setting the ratio in melt viscosity of N6 to the copolymerized PETat 0.9 and the amount of terminal amino groups at 6.5×10⁻³ molarequivalent per gram of N6. The N6 in the polymer alloy contained a largeamount of terminal amino groups (6.2×10⁻³ molar equivalent per gram).Thus, the fiber showed somewhat lower spinnability than that in Example1, although it is trivial as showing two yarn breakings duringcontinuous spinning for 24 hours. The resulting highly oriented undrawnyarn exhibited somewhat large yarn unevenness and had a U % of 2%. Thehighly oriented undrawn yarn had a strength of 2.5 cN/dtex. Untwistingin the draw false-twisting process was somewhat unstable and theresulting yarn showed some not-untwisted untwisted portions as comparedwith Example 1.

The resulting crimped polymer alloy yarns were free from coarselyaggregated polymer particles. The area ratio of islands each having adiameter of 200 nm or more to the total islands was 0.1% or less, andthe area ratio of islands each having a diameter of 20 nm or more was 1%or less. The islands-part polymer constituted a lined structure. Thecrimped yarn had a CR of 32% but exhibited somewhat large yarnunevenness of a U % of 2.2% due to large yarn unevenness duringspinning, as compared with Example 1. The physical properties of thefalse-twisted yarn are shown in Table 2.

The crimped polymer alloy yarn was subjected to circular knitting by theprocedure of Example 1, and 99% or more of the copolymerized PET wasremoved from the resulting round braid by an alkali treatment, tothereby obtain a round braid comprising a nanoporous N6 fiber havingunconnected pores each having a diameter of 100 nm or less. The roundbraid comprising the nanoporous N6 fiber was dyed and was found to haveexcellent color property but exhibit some dyeing speck. The nanoporousN6 fiber had excellent physical properties as shown in Table 2.

Example 6

The polymer alloy prepared according to Example 1 was subjected to meltspinning in the same way as Example 1. A spinneret used in thisprocedure contained a weighing section 18 having a diameter of 0.2 mm onthe top of a discharge orifice as shown in FIG. 30 and had an orificediameter 20 of 0.5 mm and an orifice length 19 of 1.25 mm. The dischargerate per one orifice was set at 2.1 g per minute, and the linearvelocity of the discharged polymer alloy in the spinneret was set at 10meters per minute. The yarn could be satisfactorily spun without anyyarn breaking during continuous spinning for 24 hours. The yarn did notcause deformation of the wound package due to swelling with time, whichconstitutes a problem in regular nylon yarns, and showed goodhandleability. This was then subjected to draw false-twisting by theprocedure of Example 1, except for setting the draw ratio at 1.3.

The resulting 50 dtex, 12-filament false-twisted yarn exhibitedexcellent physical properties including a strength of 3.5 cN/dtex, anelongation percentage of 29%, a thermal shrinkage of 8% and a CR of 38%(Table 2). The cross section of the crimped polymer alloy yarn wasobserved under a TEM and was found that the yarn had an islands-in-seastructure comprising N6 as a sea (dark region) and the copolymerized PETas islands (bright regions). The islands had an average diameter of 25nm, showing that the polymer alloy fiber comprises the copolymerized PEThomogeneously dispersed with size on the order of nanometers. The arearatio of islands each having a diameter of 200 nm or more to the totalislands was 1% or less. The TEM observation of the longitudinal sectionof the fiber shows that the islands has a lined structure. The physicalproperties of the false-twisted yarn are shown in Table 2.

A round braid was prepared by using the crimped polymer alloy yarn as anS-twist/Z-twist two ply yarn and was immersed in a 3% aqueous sodiumhydroxide solution (90° C., liquor ratio of 1:100) for one hour tothereby remove 99% or more of the copolymerized PET in the polymer alloyfiber upon hydrolysis. After washing with water and drying, a roundbraid comprising a nanoporous N6 fiber was obtained.

The cross section of the nanoporous N6 fiber was observed under a TEM tofind that the fiber contained no coarse pores each having a diameter of50 nm or more and had an average diameter of pores of 25 nm. In the TEMobservation, the dark region corresponds to the N6 polymer, and thebright regions correspond to the pores, showing that the pores areunconnected pores.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property. In addition, this article had aratio of moisture adsorption (ΔMR) of 5.6% and showed much higherhygroscopicity than cotton. The article had a strength of 2.6 cN/dtexand an elongation percentage of 30%, showing to have sufficientmechanical properties as a fibrous article. This exhibited reversiblewater swelling, and the yarn sampled from the round braid comprising thenanoporous N6 fiber after setting at 180° C. for one minute had apercentage of swelling in a longitudinal direction of the yarn of 7%.The physical properties of the nanoporous N6 fiber are shown in Table 1.

Example 7

Materials were subjected to melt kneading, melt spinning and drawfalse-twisting by the procedure of Example 6, except for using a N6having a melt viscosity of 1260 poises (280° C. at a rate of shear of2432 sec⁻¹) and containing terminal amino groups in an amount of5.0×10⁻⁵ molar equivalent per gram of N6, setting the ratio in meltviscosity at 0.9 and changing the discharge rate per one orifice and thenumber of spinneret orifices. The resulting 105 dtex, 96-filamentcrimped polymer alloy yarn had a strength of 3.8 cN/dtex, an elongationpercentage of 29%, a thermal shrinkage of 8% and a CR of 35% (Table 2).The cross section of the fiber of the crimped polymer alloy yarn wasobserved under a TEM, to find that the yarn was free from coarselyaggregated polymer particles, that the area ratio of islands each havinga diameter of 200 nm or more to the total islands was 0.1% or less, andthat the area ratio of islands each having a diameter of 100 nm or morewas 1% or less. The TEM observation of the longitudinal section of thefiber shows that the islands has a lined structure.

A round braid was prepared by using the crimped polymer alloy yarn as anS-twist/Z-twist two ply yarn by the procedure of Example 1, from which99% or more of the copolymerized PET was removed by an alkali treatment,to thereby obtain a round braid comprising a nanoporous N6 fiber.

The cross section of the nanoporous N6 fiber was observed under a TEM,to find that pores from which the islands-part polymer had been removedhad an average diameter of 20 nm and were free from coarse pores eachhaving a diameter of 50 nm or more. The pores were unconnected pores.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The nanoporous N6 fiber hasexcellent physical properties as shown in Table 1. TABLE 1 Average poreArea Area Percentage of diameter ratio 1 ratio 2 Strength ΔMR ColorAdsorbing water (nm) (%) (%) (cN/dtex) (%) property rate (%) retention(%) Example 1 25 0 0 2.0 5.6 Excellent 60 85 Example 2 25 0 0 3.8 3.6Excellent 45 67 Example 3 25 0 0 3.0 4.2 Excellent 52 76 Example 4 25 00 2.0 6.0 Excellent 62 90 Example 5 20 0 0 1.8 5.0 Good 55 80 Example 625 0 0 2.6 5.6 Excellent 60 82 Example 7 20 0 0 3.0 5.5 Excellent 60 82Average pore diameter: Average pore diameter estimated based on TEMobservationArea ratio 1: Area ratio of pores having a diameter of 200 nm or more tothe total fiberArea ratio 2: Area ratio of pores having a diameter of 50 nm or more tothe total fiberAdsorbing rate: Ammonia adsorbing rate

TABLE 2 N6 polymer Average NH₂ Area diameter of Thermal concentrationratio islands Strength CR U % shrinkage (mol/g) wt % (%) (nm)Spinnability (cN/dtex) (%) (%) (%) Example 1 5.0 × 10⁻⁵ 80 0.1 or 25Good 2.7 38 1.0 8 less Example 2 5.0 × 10⁻⁵ 95 0.1 or 20 Good 4.0 45 0.812 less Example 3 5.0 × 10⁻⁵ 90 0.1 or 25 Good 3.5 40 0.9 11 lessExample 4 5.0 × 10⁻⁵ 50 0.1 or 18 Good 2.5 35 1.2 8 less Example 5 6.5 ×10⁻⁵ 80 0.1 or 20 Fair 2.5 32 2.2 9 less Example 6 5.0 × 10⁻⁵ 80 0.1 or25 Good 3.5 38 1.5 8 less Example 7 5.0 × 10⁻⁵ 80 0.1 or 20 Good 3.8 351.5 8 lessArea ratio: Area ratio of pores having a diameter of 200 nm or more tothe total islands

Example 8

The N6 and the copolymerized PET used in Example 1 were melted at 270°C. and 290° C., respectively using an apparatus shown in FIG. 31 andwere divided and mixed at 104×10⁴ splits by a static mixer 21(“Hi-Mixer”, available from Toray Engineering Co., Ltd., 10 steps)arranged in a pack 3. The mixture was filtrated through a metallicnonwoven fabric filter having an absolute filtration diameter of 20 μmand was discharged from spinneret orifices each having a diameter of0.35 mm at a spinning temperature of 280° C. and a distance from thespinneret 4 to the top of the cooling equipment 5 of 7 cm. The resultingarticle was drawn at a spinning rate of 900 meters per minute and waswound via a second take-up roller 9. The fiber showed good spinnabilitywithout any yarn breaking during continuous spinning for 24 hours. Thisarticle was then subjected to draw thermal treatment using a deviceshown in FIG. 32 at a draw ratio of 3.2, a temperature of a first hotroller 24 of 70° C. and a temperature of a second hot roller 25 of 130°C. The fiber showed good drawability without any yarn breaking duringthe draw thermal treatment.

Thus, a 56 dtex, 12-filament polymer alloy fiber having a U % of 1.5%was prepared. The cross section of the fiber was observed under a TEM tofind that an N6 portion dyed thick and a PET portion dyed thin by metalstaining constituted a special layered structure, and the PET layer hada thickness of about 20 nm (FIG. 8). In a portion about 150 nm deep fromthe fiber surface layer, the special layered structure broken and wasconverted into an islands-in-sea structure. However, the area ratio ofthe special layered structure to the total cross section of the fiberwas 98%, showing that the special layered structure occupied almost allof the fiber section (FIG. 9). The longitudinal section of the polymeralloy fiber was observed under a TEM to find that layers extended aslines (FIG. 10). The physical properties of the polymer alloy fiber areshown in Table 4.

The polymer alloy fiber was formed into a round braid with goodprocessability without any trouble in the knitting process. The roundbraid was immersed in a 3% aqueous sodium hydroxide solution at 95° C.for one hour, to completely remove the PET from the polymer alloy fiber,to thereby obtain a round braid comprising a nanoporous N6 fiber.

The round braid showed hygroscopicity in terms of ΔMR of 5.7%, muchhigher than that of cotton.

The cross section of the nanoporous fiber was observed under a TEM (FIG.11) to find that the nanoporous fiber had a finer pattern of dark regionand bright regions than the original polymer alloy fiber upon metalstaining. The dark region corresponds to a portion with high density ofN6, and the bright regions correspond to portions with a low density ofN6. The bright regions are considered to correspond to pores. The poreshave an average diameter of 10 to 20 nm. These results show that thefiber was free from coarse pores each having a diameter of 50 nm ormore. FIG. 11 does not clearly show whether the pores are unconnectedpores or connected pores, but the pores are determined as unconnectedpores, because the low density portions are arrayed in lines in theobservation of a longitudinal section (FIG. 12).

The round braid prepared from the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The nanoporous N6 fiber hadexcellent physical properties as shown in Table 3.

Example 9

The N6 and the copolymerized PET were subjected to melt spinning by theprocedure of Example 8, except for blending 50% by weight of N6 and 50%by weight of the copolymerized PET. The fiber showed good spinnabilitywithout any yarn breaking during continuous spinning for 24 hours. Thisarticle was subjected to draw thermal treatment by the procedure ofExample 8 and showed good drawability without any yarn breaking.

The cross section of the polymer alloy fiber was observed under a TEM,and the result is shown in FIG. 13. The copolymerized PET constitutedbeaded islands comprising connected fine islands each having a diameterof about 10 to 20 nm and was free from coarsely aggregated polymerparticles. The area ratio of islands each having a diameter of 200 nm ormore to the total islands was 0.1% or less, and the area ratio ofislands each having a diameter of 100 nm or more was 1% or less. The TEMobservation of the longitudinal section of the fiber shows that theislands has a lined structure. The yarn had excellent physicalproperties as shown in Table 4.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 8, from which 99% or more of the cepolymerized PETwas removed by an alkali treatment, to thereby obtain a round braidcomprising a nanoporous N6 fiber.

The cross section of the nanoporous N6 fiber observed under a TEM isshown in FIG. 14, showing a fine thick-thin pattern (dark and lightpattern) of about 10 to 20 nm and pores each having a diameter of 20 nmor less. The average diameter of pores is estimated from this result asbeing 10 to 20 nm. The observation of the longitudinal section of thefiber (FIG. 15) shows unclear lines, indicating that the pores areconnected with each other to form connected pores. Thus, nanoporousfibers having connected pores can be obtained only by employing thespecific combination of polymers, specific kneading procedure andspecific blending ratio.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The nanoporous N6 fiber hadexcellent physical properties as shown in Table 3.

Example 10

The polymer alloy prepared according to Example 1 was subjected to meltspinning by the procedure of Example 1, except for changing thedischarge rate and the number of spinneret orifices, and setting thespinning rate at 900 meters per minute. The residence time from themelting section 2 to discharge was 12 minutes. The yarn could besatisfactorily spun without any yarn breaking during continuous spinningfor 24 hours. The yarn did not cause deformation of the wound packagedue to swelling with time, which constitutes a problem in regular nylonyarns, and showed good handleability. This article was subjected to drawthermal treatment by the procedure of Example 8, except for setting thedraw ratio at 3.2, the temperature of the first hot roller 24 at 70° C.and the temperature of the second hot roller 25 at 130° C. (FIG. 32) Theresulting 70 dtex, 34-filament polymer alloy fiber had excellentproperties including a strength of 3.7 cN/dtex, an elongation percentageof 47%, a U % of 1.2% and a thermal shrinkage of 11%.

The cross section of the polymer alloy fiber was observed under a TEM tofind that the fiber had an islands-in-sea structure comprising N6 as asea (dark region) and the copolymerized PET as islands (bright region)(FIG. 16). The islands had an average diameter of 38 nm. These resultsshow that the resulting polymer alloy fiber comprises the copolymerizedPET ultrafinely dispersed. The area ratio of islands each having adiameter of 200 nm or more to the total islands was 1.2%. The TEMobservation of the longitudinal section of the fiber shows that theislands has a lined structure (FIG. 17). The physical properties of thepolymer alloy fiber are shown in Table 4.

A round braid was prepared by using the polymer alloy fiber and immersedin a 3% aqueous sodium hydroxide solution (90° C., liquor ratio of1:100) for one hour to thereby remove 99% or more of the copolymerizedPET from the polymer alloy fiber upon hydrolysis, followed by washingwith water and drying.

The side of the nanoporous N6 fiber was observed with an opticalmicroscope, to find that the fiber had a diameter somewhat lower thanthat of the fiber before the alkali treatment, showing that the fibershrank in its radius direction as a result of the removal of theislands-part polymer.

The side of the nanoporous N6 fiber was observed under a SEM to findthat the fiber had a smooth surface without unevenness at amagnification of about 2000 times. The cross section of the nanoporousN6 fiber was observed under a TEM (FIG. 18) to find that the fiber had apattern of dark and bright regions finer than that of the originalpolymer alloy fiber (FIG. 16) upon metal staining. The dark regions areregions at high density of N6, and bright regions are regions at lowdensity of N6. The bright regions are considered to correspond to pores.These results show that the pores each have a smaller size than theoriginal islands-part polymer as a result of the removal of theislands-part polymer, have an average diameter of 10 to 20 nm and arefree from coarse pores each having a diameter of 50 nm or more. Thepatterns of dark and bright regions in FIG. 18 (the cross section of thefiber) and FIG. 19 (the longitudinal section of the fiber) show thatthese pores are unconnected pores.

The round braid prepared from the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The ratio of moisture adsorption(ΔMR) was 6%, showing much higher hygroscopicity than cotton. Thenanoporous N6 fiber had a strength of 2.0 cN/dtex and an elongationpercentage of 70%, showing that the fiber had sufficient mechanicalproperties as a fibrous article. The physical properties of thenanoporous N6 fiber are shown in Table 3.

Example 11

The N6 and the copolymerized PET were subjected to melt kneading by theprocedure of Example 1, except for blending 40% by weight of N6 and 60%by weight of the copolymerized PET, to thereby obtain master pellets.The pellets had an average weight per pellet of 3 mg and an amount ofterminal amino groups of 3.5×10⁻⁵ molar equivalent per gram of N6.

The master pellets and the virgin N6 pellets (average weight per pelletof 3 mg) used in melt kneading were charged into different hoppers 1,weighed in weighing sections 28, respectively, and fed to a blendingtank 29 having a capacity of 7 kg (FIG. 33). The blending ratio of themaster pellets to the virgin N6 pellets was 1/3 by weight, and 20 ppm ofan antistatic agent·(EMULMIN 40 available from Sanyo ChemicalIndustries, Ltd.) was incorporated for preventing adhesion of pellets tothe wall of the blending tank. The pellets were blended in the blendingtank, fed to a twin-screw extrusion-kneader 30 and subjected to meltkneading, to thereby obtain a polymer alloy comprising 15% by weight ofthe copolymerized PET. In this procedure, the length of the kneadingsection was set at 33% of the effective length of the screws, and thekneading temperature was set at 260° C. The polymer alloy was subjectedto melt spinning by the procedure of Example 1, to obtain a highlyoriented undrawn yarn. The yarn could be satisfactorily spun without anyyarn breaking during continuous spinning for 24 hours. The yarn did notcause deformation of the wound package due to swelling with time, whichconstitutes a problem in regular nylon yarns, and showed goodhandleability. The undrawn polymer alloy yarn showed excellent physicalproperties of a strength of 2.5 cN/dtex, an elongation percentage of130% and a U % of 1.4%. This article was subjected to draw thermaltreatment by the procedure of Example 8, except for setting the drawratio at 1.5, the temperature of the first hot roller 24 at 90° C. andthe temperature of the second hot roller 25 at 130° C. The polymer alloyfiber was of 87 dtex and 24 filaments and had excellent physicalproperties of a strength of 3.2 cN/dtex, an elongation percentage of33%, a thermal shrinkage of 8% and a U % of 1.6% (Table 4). The crosssection of the polymer alloy fiber was observed under a TEM to find thatthe fiber had an islands-in-sea structure comprising N6 as a sea (darkregion) and the copolymerized PET as islands (bright region). Theislands had an average diameter of 45 nm. These results show that theresulting polymer alloy fiber comprises the copolymerized PETultrafinely dispersed. The area ratio of islands each having a diameterof 200 nm or more to the total islands was 1.6%. The TEM observation ofthe longitudinal section of the fiber shows that the islands has a linedstructure.

This article was knitted into a round braid of 20 G and treated with a3% by weight aqueous sodium hydroxide solution (95° C., liquor ratio of1:50) for one hour, to dissolve off and remove 99% or more of thecopolymerized PET from the polymer alloy fiber.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property but to show slight dyeing speck.The article had a ratio of moisture adsorption (ΔMR) of 5.0% andexhibited much higher hygroscopicity than cotton.

The cross section of the nanoporous N6 fiber was observed under a TEM tofind that the fiber had unconnected pores having a diameter of about 20to 50 nm. The pores had an average diameter of 30 nm, and the area ratioof coarse pores each having a diameter of 50 nm or more was 1.0%. Theround braid had a strength of 2.0 cN/dtex and an elongation percentageof 25%, showing that the round braid had sufficient mechanicalproperties as a fibrous article. The physical properties of thenanoporous N6 fiber are shown in Table 3.

Example 12

The N6 and the copolymerized PET used in melt kneading in Example 1 werecharged into different hoppers 1, weighed in weighing sections 28,respectively, and fed to a blending tank 29 having a capacity of 7 kg(FIG. 33). The N6 and the copolymerized PET were used in amounts of 85%by weight and 15% by weight, respectively, and 20 ppm of an antistaticagent (EMULMIN 40 available from Sanyo Chemical Industries, Ltd.) wasincorporated for preventing adhesion of pellets to the wall of theblending tank. The pellets were blended in the blending tank, fed to atwin-screw extrusion-kneader 30 and subjected to melt kneading, tothereby obtain a polymer alloy. In this procedure, the length of thekneading section was set at 33% of the effective length of the screws,and the kneading temperature was set at 260° C. The polymer alloy wassubjected to melt spinning by the procedure of Example 1, to obtain ahighly oriented undrawn yarn. Broken end occurred once during continuousspinning for 24 hours. The yarn did not cause deformation of the woundpackage due to swelling with time, which constitutes a problem inregular nylon yarns, and showed good handleability. The undrawn polymeralloy yarn showed excellent physical properties of a strength of 2.4cN/dtex, an elongation percentage of 125% and a U % of 1.6%. The yarnwas subjected to draw false-twisting by the procedure of Example 1 butshowed somewhat unstable untwisting as compared with Example 1. Theresulting 87 dtex 24-filament false-twisted yarn had a strength of 2.4cN/dtex, an elongation percentage of 21%, a thermal shrinkage of 9%, a U% of 2.2% and a CR of 30% showed some but trivial not-untwisted portionsas compared with Example 1 (Table 4). The cross section of the crimpedpolymer alloy yarn was observed under a TEM to find that the yarn had anislands-in-sea structure comprising N6 as a sea (dark region) and thecopolymerized PET as islands (bright region). The islands had an averagediameter of 52 nm, showing that the polymer alloy fiber comprised thecopolymerized PET ultrafinely dispersed. The area ratio of islands eachhaving a diameter of 200 nm or more to the total islands was 2.0%. TheTEM observation of the longitudinal section of the fiber shows that theislands has a lined structure.

This was knitted into a round braid of 20 G and treated with a 3% byweight aqueous sodium hydroxide solution (95° C., liquor ratio of 1:50)for one hour to thereby dissolve off and remove 99% or more of thecopolymerized PET from the false-twisted polymer alloy yarn.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property but show some dyeing speck. Theround braid had a ratio of moisture adsorption (ΔMR) of 5.0% andexhibited much higher hygroscopicity than cotton.

The cross section of the nanoporous N6 fiber was observed under a TEM tofind that the fiber had unconnected pores each having a diameter ofabout 20 to 50 nm. The average of the pores was 35 nm, and the arearatio of coarse pores each having a diameter of 50 nm or more was 1.6%.The fiber had a strength of 1.8 cN/dtex and an elongation percentage of25%, showing that the fiber had sufficient mechanical properties as afibrous article. The physical properties of the nanoporous N6 fiber areshown in Table 3.

Example 13

The melt spinning procedure of Example 10 was carried out to conductspinning and direct drawing using a device shown in FIG. 34, except forchanging the discharge rate per one orifice and the number of spinneretorifices and setting the circumferential speed of a first hot roller 31at 2000 meters per minute, the temperature of the first hot roller 31 at40° C., the circumferential speed of a second hot roller 32 at 4500meters per minute and the temperature of the second hot roller 32 at150° C. Thus, a 55 dtex 12-filament polymer alloy fiber having astrength of 4.4 cN/dtex, an elongation percentage of 37%, a U % of 1.2%and a thermal shrinkage of 12% was prepared. The fiber showed goodspinnability without any yarn-breaking during continuous spinning for 24hours. The resulting polymer alloy fibers were free from coarselyaggregated polymer particles. The area ratio of islands each having adiameter of 200 nm or more was 0.1% or less, and the area ratio ofislands each having a diameter of 100 nm or more was 1% or less. The TEMobservation of the longitudinal section of the fiber shows that theislands has a lined structure. The, yarn had excellent physicalproperties as shown in Table 4.

The polymer alloy fibers were subjected to circular knitting by theprocedure of Example 10, from which 99% or more of the copolymerized PETwas removed by an alkali treatment, to thereby obtain a round braidcomprising a nanoporous N6 fiber.

The cross section of the nanoporous N6 fiber was observed under a TEM tofind that the fiber had dark and bright regions as a result of metalstaining finer than the original polymer alloy fiber, showing that thepores had sizes smaller than the original islands-part polymer as aresult of the removal of the islands-part polymer, and that the averagediameter of the pores was 10 to 20 nm and were free from coarse poreseach having a diameter of 50 nm or more. The TEM observation shows thatthese pores are unconnected pores. The round braid comprising thenanoporous N6 fiber was dyed and was found to have excellent colorproperty. The nanoporous N6 fiber had excellent physical properties asshown in Table 3.

Comparative Example 1

Melt spinning was carried out by the procedure of Example 1, except forkneading the materials by simple chip blending (dry blending) with theuse of a device shown in FIG. 28 instead of the twin-screwextrusion-kneader. As a result, the polymers showed poor spinnability,could not be stably discharged during spinning and often invited yarnbreakings during spinning. Thus, a yarn could not be stably wound.Accordingly, the spinning rate was changed to 900 meters per minute,which failed to wound a yarn stably. However, the resulting nominalundrawn yarn was subjected to draw thermal treatment at a draw ratio of3.2, a temperature of the first hot roller 24 of 70° C. and atemperature of the second hot roller 25 of 130° C., to obtain a polymeralloy fiber. The cross section of the polymer alloy fiber was observedunder a TEM to find that uneven blending was significant, some coarselyaggregated polymer particles were observed, and the area ratio ofislands each having a diameter of 200 nm or more to the total islandswas 10% (Table 4). A round braid was prepared from this and wassubjected to an alkali treatment by the procedure of Example 6 to obtaina porous N6 fiber. This fiber, however, had a large area ratio of coarsepores each having a diameter of 200 nm or more of 2.0%, scattered alarge quantity of light, appeared whitish and exhibited poor colorproperty (Table 3).

The above-prepared polymer alloy fiber was subjected to false twistingusing a spinner pin as a rotator 15, at a temperature of a heater 13 of165° C. and a draw ratio of 1.01, which invited unstable untwisting andfrequent yarn breakings. The resulting nominal false-twisted yarn had amarkedly large amount of not-untwisted portions and exhibited poorquality.

Comparative Example 2

The materials were subjected to melt kneading by the procedure ofExample 1, except for setting the length of the kneading section at 10%of the effective length of the screws, to obtain polymer alloy chips.The chips were subjected to TEM observation to find that thecopolymerized PET was dispersed unevenly, in which some particles weredispersed with a diameter of about 30 nm but may others were dispersedwith a diameter of 100 nm or more (FIG. 20). The area ratio of coarselydispersed polymer particles each having a diameter in terms of circle of100 nm or more was 50% or more to the total dispersed polymer in a crosssection of the pellet.

The polymer alloy pellets were subjected to melt spinning by theprocedure of Example 1, but showed poor spinnability and invitedfrequent yarn breakings during spinning, and a yarn could not be stablywound. Accordingly, the spinning rate was changed to 900 meters perminute, which failed to wound a yarn stably. The resulting nominalundrawn yarn was subjected to draw thermal treatment by the procedure ofComparative Example 1, to obtain a polymer alloy fiber. The crosssection of the polymer alloy fiber was observed under a TEM to find thatthe fiber showed significant uneven blending, had some coarselyaggregated polymer particles, in which the area ratio of islands eachhaving a diameter of 200 nm or more to the total islands was 8% (Table4). A round braid was prepared from this and was subjected to an alkalitreatment by the procedure of Comparative Example 1, to obtain a porousN6 fiber. The resulting porous fiber, however, had a large area ratio ofcoarse pores each having a diameter of 200 nm or more of 1.9%, scattereda large quantity of light, appeared whitish and exhibited poor colorproperty (Table 3).

The resulting polymer alloy fiber was subjected to false twisting by theprocedure of Comparative Example 1, but invited unstable untwisting andfrequent yarn breakings. The resulting nominal false-twisted yarn had amarkedly large amount of not-untwisted portions and exhibited poorappearance quality. TABLE 3 Area Area Percentage of Average pore ratio 1ratio 2 Strength ΔMR Color Adsorbing water diameter (nm) (%) (%)(cN/dtex) (%) property rate (%) retention (%) Example 8 20 or less 0 02.1 5.7 Excellent 60 83 Example 9 20 or less 0 0 2.0 3.6 Excellent 62 84Example 10 20 or less 0 0 2.0 6.0 Excellent 60 83 Example 11 30 0 1.02.0 5.0 Good 58 80 Example 12 35 0 1.6 1.8 5.0 Good 55 80 Example 13 20or less 0 0 3.4 5.8 Excellent 60 80 Comparative — 2.0 — 1.3 4.3 Failure— — Example 1 Comparative — 1.9 — 1.3 4.2 Failure — — Example 2Average pore diameter: Average pore diameter estimated based on TEMobservationArea ratio 1: Area ratio of pores having a diameter of 200 nm or more tothe total fiberArea ratio 2: Area ratio of pores having a diameter of 50 nm or more tothe total fiberAdsorbing rate: Ammonia adsorbing rate

TABLE 4 Average Thermal Kneading Area ratio diameter of Strengthshrinkage procedure (%) islands (nm) Spinnability (cN/dtex) U % (%) (%)Example 8 Static 0.1 or less 20 (thick) Good 3.5 1.5 12 Example 9 Static0.1 or less 15 Good 3.2 1.5 12 Example 10 EXT 1.2 38 Good 3.7 1.2 11Example 11 Blending 1.6 45 Good 3.2 1.6 8 tank → EXT Example 12 Blending2.0 52 Fair 2.4 2.2 9 tank → EXT Example 13 EXT 0.1 or less 26 Good 4.41.2 12 Comparative Chip 10 130 Failure 2.8 8.2 11 Example 1 blendingComparative EXT 8 120 Failure 2.8 8.0 11 Example 2Area ratio: Area ratio of pores having a diameter of 200 nm or more tothe total islandsStatic: Static mixer (having a number of splits of 104 × 10⁴)EXT: twin-screw extrusion-kneaderBlending tank → EXT: Twin-screw extrusion-kneader after chip blending asmall amount of materials in a blending tankChip blending: Dry blending of pellets

Example 14

N6 and the copolymerized PET were subjected to melt kneading, meltspinning, and draw thermal treatment by the procedure of Example 10,except for using a high-viscosity N6 having a melt viscosity of 1540poises (280° C. at a rate of shear of 2432 sec⁻¹) and containingterminal amino groups in an amount of 5.0×10⁻⁵ molar equivalent pergram, setting the blending ratio of N6 to the copolymerized PET at 1.1,and changing the discharge rate per one orifice and the number ofspinneret orifices, to thereby obtain 105 dtex, 96-filament polymeralloy fibers. They showed good spinnability and were free from yarnbreaking during continuous spinning for 24 hours. The resulting polymeralloy fibers were free from coarsely aggregated polymer particles, inwhich the area ratio of islands each having a diameter of 200 nm or morewas 0.1% or less, and the area ratio of islands each having a diameterof 100 nm or more was 1% or less. The yarn had excellent physicalproperties as shown in Table 6. The longitudinal section of the fiberwas observed under a TEM, to find that the islands had a linedstructure.

The polymer alloy fibers were subjected to circular knitting, from which99% or more of the copolymerized PET was removed by an alkali treatmentby the procedure of Example 10, to thereby obtain a round braidcomprising a nanoporous N6 fiber.

The nonporous N6 fiber was observed with an optical microscope and anSEM, respectively, to find that the fiber shrank in its radius directionas a result of the removal of the islands-part polymer, and the fiberhad a smooth surface without unevenness at a magnification of about 2000times. The cross section of the nanoporous N6 fiber was observed under aTEM to find that the fiber had dark and bright regions as a result ofmetal staining finer than the original polymer alloy fiber, showing thatthe pores had sizes smaller than the original islands-part polymer as aresult of the removal of the islands-part polymer, and that the averagediameter of the pores was 10 to 20 nm and were free from coarse poreseach having a diameter of 50 nm or more. The pores were unconnectedpores.

The round braid comprising the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The nanoporous N6 fiber hadexcellent physical properties as shown in Table 5.

Example 15

The N6 used in Example 10 (50% by weight) and a PET copolymerized with12% by mole of 5-sodiosulfoisophthalic acid and 26% by mole ofisophthalic acid (50% by weight) were kneaded in a twin-screwextrusion-kneader at 245° C., to thereby obtain polymer alloy chips. Thepolymer alloy was subjected to melt spinning by the procedure of Example3, except for setting the spinning temperature at 250° C. and thespinneret diameter at 0.6 mm and changing the discharge rate per oneorifice, and the resulting undrawn yarn was wound at a spinning rate of800 meters per minute. This was subjected to draw thermal treatment at adraw ratio of 3.4, a temperature of the first hot roller 24 of 90° C.and a temperature of the second hot roller 25 of 130° C., to therebyobtain a 85 dtex, 36-filament polymer alloy yarn. The yarn could besatisfactorily spun without any yarn breaking during continuous spinningfor 24 hours. The cross section of the polymer alloy fiber was observedunder a TEM, and the result is shown in FIG. 21. The copolymerized PETconstituted islands in the form of layers having a minor axis of about10 to 30 nm and a major axis of about 50 to 100 nm and was free fromcoarsely aggregated polymer particle. The area ratio of islands eachhaving a diameter of 200 nm or more to the total islands was 0.1% orless, and the area ratio of islands each having a diameter of 100 nm ormore was 1% or less. The TEM observation of the longitudinal section ofthe fiber shows that the islands has a lined structure. The yarn hadexcellent physical properties as shown in Table 6.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 10 and treated with a 3% by weight aqueous sodiumhydroxide solution (90° C., liquor ratio of 1:50) for one hour todissolve off and remove 99% or more of the copolymerized PET, to therebyobtain a round braid comprising a nanoporous N6 fiber. The fibersignificantly shrank in its radius direction-with a shrinkage in radiusdirection of about 22% and a shrinkage in terms of cross sectional areaof about 40%. The side of the constitutional fiber of the nylon 6 yarnafter removing the copolymerized PET was observed with an SEM (2000times) and was found neither streaky grooves nor voids from which thecopolymerized PET had been removed.

The cross section of the nanoporous N6 fiber was observed under a TEM,and the result is shown in FIG. 22, showing that the average diameter ofthe pores was 10 to 20 nm and were free from coarse pores each having adiameter of 50 nm or more. These pores were considered to be connectedwith each other to form connected pores.

The round braid prepared from the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The water swelling of thenanoporous N6 fiber was determined to find that the yarn had a highpercentage of swelling in its longitudinal direction of 11.1%. Thearticle showed substantially no decrease in percentage of swelling in alongitudinal direction of the yarn even in a third measurement andexhibited satisfactory reversibility and durability. The water swellingof the nanoporous N6 fiber was determined again after heat treating theround braid at 160° C. for 10 minutes. The fiber showed a somewhatdecreased percentage of swelling in the longitudinal direction of theyarn of 7.3% as compared with that before thermal treatment, which is,however, significantly larger than that of regular N6 fibers, 3%. Thisindicates that the percentage of swelling in a longitudinal direction ofthe yarn can be controlled by a thermal treatment, which facilitates thedesigning of fabrics. The nanoporous N6 fiber had excellent physicalproperties as shown in Table 5.

Example 16

The melt spinning, draw thermal treatment procedure of Example 10 was,repeated, except for using, as the copolymerized PET, a copolymerizedPET having a melting point of 225° C., containing 0.05% by weight oftitanium oxide and being copolymerized with 7% by mole of isophthalicacid and 4% by mole of an ethylene oxide adduct of bisphenol A, forusing 50% by weight of N6 and 50% by weight of the copolymerized PET,and setting the spinneret diameter at 0.7 mm. The spinning was somewhatunstable as compared that in Example 10, but it was trivial, and yarnbreaking occurred twice during continuous spinning for 24 hours. Thecross section of the polymer alloy fiber was observed under a TEM, andthe result is shown in FIG. 23. The fiber had little coarsely aggregatedpolymer particles, but the average diameter of islands was 143 nm, andthe area ratio of islands each having a diameter of 200 nm or more tothe total islands was 5%. The TEM observation of the longitudinalsection of the fiber shows that the islands has a lined structure. Thephysical properties of the yarn are shown in. Table 6.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 10, from which 99% or more of the copolymerized PETwas removed by an alkali treatment, to thereby obtain a round braidcomprising a nanoporous N6 fiber.

The nanoporous N6 fiber was observed with an optical microscope to findthat the fiber shrank in its radius direction as a result of the removalof the islands-part polymer, as in Example 10. The cross section of thenanoporous N6 fiber was observed under a TEM, and the result is shown inFIG. 24. Holes from which the islands-part polymer had been removed werecrushed to form pores having a width of about 10 to 30 nm and a lengthof about 100 nm including some coarse pores each having a diameter of 50to 100 nm. However, the area ratio of coarse pores each having adiameter of 200 nm or more was 0.5%. The color property of this articlewas determined to find that the article had color property at usablelevel for clothing, although it was inferior to that in Example 10. Thepores of the fiber were unconnected pores.

Example 17

The melt kneading procedure of Example 1 was repeated, except for using,instead of the copolymerized PET, a polyalkylene oxide derivative,“Paogen PP-15” available from Daiichi Kogyo Seiyaku Co., Ltd., servingas a polymer soluble in hot water and setting the temperature at 240° C.The resulting polymer alloy chip had b* of 4.5. The kneaded product wassubjected to melt spinning, draw thermal treatment by the procedure ofExample 10, except for changing the discharge rate per one orifice andthe number of spinneret orifices and setting a spinning rate at 4000meters per minute and a draw ratio at 1.2, to thereby obtain a 55 dtex,68-filament polymer alloy fiber. The yarn could be satisfactorily spunwithout any yarn breaking during continuous spinning for 24 hours. Thecross section of the polymer alloy fiber was observed under a TEM tofind that the fiber was free from coarsely aggregated polymer particles,and the area ratio of islands each having a diameter of 200 nm or moreto the total islands was 1.3%. The islands-part polymer was dispersed aslines. The yarn had excellent physical properties as shown in Table 6.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 10 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain a round braid comprising a nanoporous N6 fiber.

The cross section of the nanoporous N6 fiber was observed under a TEM,to find that the pores were unconnected pores, had an average diameterof 30 nm and were free from coarse pores each having a diameter of 50 nmor more. The pores of this fiber were unconnected pores.

The round braid prepared from the nanoporous N6 fiber was dyed and wasfound to have excellent color property. The nanoporous N6 fiber hadexcellent physical properties as shown in Table 5.

Example 18

The melt kneading procedure of Example 1 was repeated, except for using,instead of the copolymerized PET, a poly(L-lactic acid) having anoptical purity of 99.5% or more, a weight-average molecular weight of15×10⁴, a melt viscosity of 857 poises (240° C., 2432 sec⁻¹) and amelting point of 170° C. and setting the kneading temperature at 220° C.The weight-average molecular weight of the polylactic acid wasdetermined in the following manner. A solution of a sample in chloroformwas mixed with THF (tetrahydrofuran) to obtain a specimen solution. Thespecimen solution was subjected to measurement at 25° C. using a gelpermeation chromatograph (GPC) Waters 2690 available from Waters, andthe weight-average molecular weight in terms of polystyrene wasdetermined. The N6 used in Example 1 had a melt viscosity of 570 poisesat 240° C., 2432 sec⁻¹. The kneaded product was subjected to meltspinning by the procedure of Example 1, except for changing thedischarge rate per one orifice and the number of spinneret orifices andsetting the spinning rate at 3500 meters per minute, to thereby obtain ahighly oriented undrawn yarn of 105 dtex, 36 filaments having a strengthof 3.1 cN/dtex, an elongation percentage of 107% and a U % of 1.2%. Theyarn could be satisfactorily spun without any yarn breaking duringcontinuous spinning for 24 hours. This was subjected to drawfalse-twisting by the procedure of Example 1, except for setting thedraw ratio at 1.4 to thereby obtain a 76 dtex, 36-filament false-twistedyarn having a strength of 4.0 cN/dtex, an elongation percentage of 29%,a U % of 1.3% and a CR of 35%. In this procedure, the temperature of theheater was set at 160° C. in consideration of the melting point of thepoly(L-lactic acid). Thus, the resulting false-twisted yarn wassubstantially free from not-untwisted portions, had excellent appearancequality and exhibited good processability in draw false-twisting. Thecross section of the fiber of the crimped polymer alloy yarn wasobserved under a TEM to find that the fiber was free from coarselyaggregated polymer particles, the area ratio of islands-part polymerparticles having a diameter of 200 nm or more to the total islands partswas 0.1% or less, and the an average diameter of the islands-partpolymer was 80 nm. The yarn had excellent physical properties as shownin Table 1.

The crimped polymer alloy yarn was subjected to circular knitting and toan alkali treatment by the procedure of Example 1 to remove 99% or moreof the poly(L-lactic acid), to thereby obtain a round braid comprising ananoporous N6 fiber. The round braid prepared from the nanoporous N6fiber was dyed and was found to have excellent color property.

The cross section of the nanoporous N6 fiber sampled from the roundbraid was observed under a TEM, to find that holes from which theislands-part polymer had been removed constituted pores having adiameter of about 30 nm without coarse pores having a diameter of 50 nmor more. The resulting nanoporous fiber had a strength higher than thatin Example 1. This is probably because sulfo groups contained in thecopolymerized PET used in Example 1 may form a pseudo-crosslinkingstructure and inhibit the formation of fiber structure of N6, but PLAused herein less invites such adverse effects.

Comparative Example 3

An N6 having a relative viscosity of 2.8, a melt viscosity of 1260poises (280° C. at a rate of shear of 2432 sec⁻¹) (50% by weight) and apolyethylene terephthalate copolymerized with 2.5% by mole of5-sodiosulfoisophthalic acid and 3.5% by mole of an ethylene oxideadduct of bisphenol A (50% by weight) were subjected to simple chipblending, and the blend was melted at 290° C., discharged from aspinneret having a round orifice with a diameter of 0.6 mm and subjectedto melt spinning using a device shown in FIG. 28 at a spinning rate of1200 meters per minute. However, the polymers could not be stablydischarged during spinning, the spinnability was poor and yarn breakingsoften occurred during spinning. Thus, a yarn could not be stably wound.The resulting nominal undrawn yarn was drawn using a hot plate at 120°C. at a draw ratio of 2.7. This yielded a 85 dtex, 24-filament polymeralloy fiber. The cross section of the fiber was observed under a TEM tofind that the fiber showed significant uneven blending and containedsome coarsely aggregated polymer particle, and the area ratio of islandseach having a diameter of 200 nm-or more to the total islands was 10%.

An alkali treatment was carried out to dissolve off and remove 99% ormore of the copolymerized PET. The diameter of the fiber did notsubstantially change in this procedure. The color property of this fiberwas determined to find that the area ratio of coarse pores each having adiameter of 200 nm or tore was as large as 5.0%, the fiber therebyscattered a large quantity of light, appeared whitish and exhibited poorcolor property.

Comparative Example 4

The N6 used in Comparative Example 3 (70% by weight) and a polyethyleneterephthalate having an intrinsic viscosity of 0.60 and beingcopolymerized with 4.5% by mole of 5-sodiosulfoisophthalic acid and 8.5%by weight of a polyethylene glycol having a molecular weight of 4000(30% by weight) were subjected to simple chip blending, and the blendwas melted at 280° C., discharged from a spinneret having round orificeswith a diameter of 0.6 mm and subjected to melt spinning using a deviceshown in FIG. 28 at a spinning rate of 1000 meters per minute. However,the polymers could not be stably discharged during spinning, thespinnability was poor and yarn breakings often occurred during spinning.Thus, a yarn could not be stably wound. The resulting nominal undrawnyarn was subjected to draw thermal treatment at a draw ratio of 3.35, atemperature of the first hot roller 24 of 90° C. and a temperature ofthe second hot roller 25 of 130° C. This yielded a 85 dtex, 24-filamentpolymer alloy fiber. The cross section of the fiber was observed under aTEM to find that the fiber showed significant uneven blending andcontained some coarsely aggregated polymer particles, and the area ratioof islands each having a diameter of 200 nm or more to the total islandswas 8%.

By an alkali treatment, 90% or more of the copolymerized PET wasdissolved off from the fiber. The diameter of the fiber did notsubstantially change during this procedure. The color property of thearticle was determined, to find that the fiber scattered a largequantity of light, appeared whitish and exhibited poor color property,since the area ratio of coarse pores each having a diameter of 200 nm ormore was as large as 2.4%.

Comparative Example 5

A total of 77% by weight of the N6 used in Comparative Example 3, 20% byweight of a homo-PET, and 3% by weight of a block polyether polyamide asa compatibilizer containing 45% by weight of a polyethylene glycolsegment and 55% by weight of a poly-ε-caprolactam segment were subjectedto simple chip blending, and the blend was subjected to melt spinning bythe procedure of Example 1, except for using a device shown in FIG. 28.However, the polymers could not be stably discharged during spinning,the spinnability was poor and yarn breakings often occurred duringspinning. Thus, a yarn could not be stably wound. The resulting nominalundrawn yarn was subjected to draw thermal treatment by the procedure ofExample 1 to obtain a 77 dtex, 24-filament polymer alloy fiber. Thecross section of the fiber was observed under a TEM to find that thefiber showed significant uneven blending and contained some coarselyaggregated polymer particles, and the area ratio of islands each havinga diameter of 200 nm or more to the total islands was 14%.

Then, 99% or more of the PET was dissolved off and removed by an alkalitreatment. The diameter of the fiber did not substantially change duringthis procedure, in contrast to Example 10. The color property of thearticle was determined, to find that the fiber scattered a largequantity of light, appeared whitish and exhibited poor color property,since the area ratio of coarse pores each having a diameter of 200 nm ormore was as large as 4.6%.

Comparative Example 6

The N6 and the copolymerized PET were subjected to melt spinning by theprocedure of Comparative Example 4, except for using 25% by weight of N6and 75% by weight of the copolymerized PET. However, the polymers couldnot be stably discharged during spinning, the spinnability was poor andyarn breakings often occurred during spinning. Thus, a yarn could not bestably wound. The resulting nominal undrawn yarn was drawn using a hotplate at 120° C. at a draw ratio of 2.7, to obtain a 85 dtex,24-filament polymer alloy fiber. The cross section of the fiber wasobserved under a TEM to find that N6 lower soluble in an alkaliconstituted islands, and the copolymerized PET easily soluble in analkaline solution constituted a sea, in contrast to Comparative Example4. The fiber showed significant uneven blending and contained somecoarsely aggregated polymer particles, and the area ratio of islandseach having a diameter of 200 nm or more to the total islands was 10%.

The article was subjected to alkali treatment by the procedure ofExample 10 to remove the sea part copolymerized PET, to thereby obtain afiber comprising ultrafine N6 fibers firmly bonded. The resulting fiber,however, could not be handled in practice and its strength could not bedetermined.

The polymer alloy fiber was treated with formic acid to dissolve off theislands parts N6. However, the copolymerized PET became markedlyfragile, the resulting fiber fell into pieces and could not be handledin practice. The polymer alloy fiber did not substantially yield aporous fiber and could not achieve the objects of the present invention.

Comparative Example 7

A copolymerized PET having an intrinsic viscosity of 0.60 and beingcopolymerized with ethylene naphthalate in an amount of 10% by mole tothe total acid component, and 70% by weight of a copolymerized PETcopolymerized with a polyether imide (“ULTEM”-1000 available fromGeneral Electric Company) were kneaded using a twin screwextrusion-kneader having a diameter of 30 mm at 320° C. The resultingpolymer alloy chip was fully dried and was subjected to melt spinning ata number of spinneret orifices of 6, a discharge rate per single orificeof 0.6 g per minute, a spinning temperature of 315° C. and a spinningrate of 500 meters per minute. The spinning temperature was excessivelyhigher than the melting point of the sea part copolymerized PET, whichinvited unstable spinning and poor spinnability with ten yarn breakingsduring spinning for twelve hours. The resulting nominal undrawn yarn wasdrawn at a temperature of a preheating roller of 90° C., a temperatureof a hot plate of 120° C. and a draw ratio of 3.0, resulted in frequentyarn breakings. The resulting drawn yarn had a strength as low as 1.3cN/dtex. This is probably because the kneading temperature and thespinning temperature were excessively high for the copolymerized PETserving as a major component, and the polymer was deteriorated due tothermal decomposition. This article showed a very insufficient U % of16%.

A plain fabric was prepared by using the copolymerized PET alloy fiberas a warp and a weft, which caused frequent yarn breakings and fluffingand resulted in a woven fabric exhibiting very poor processability andinferior appearance quality. The woven fabric was treated with a 6% byweight aqueous sodium hydroxide solution at 90° C. for 2 hours, toobtain a spongy fiber. This fiber, however, had a markedly low strengthof 0.3 cN/dtex. This is probably because the copolymerized PET underwentthermal degradation and, in addition, fell into pieces due to thelong-term treatment with a high concentration alkali.

As is described above, yarns having a high strength and exhibiting lessyarn unevenness cannot be obtained satisfactorily unless suitablekneading and spinning conditions for the used polymers are set. Inaddition, a small different in solubility between the higher solublepolymer and the lower soluble polymer invites low strength.

Thus, practically usable fibers can be obtained only by optimizing thekneading, spinning and dissolving conditions for individual polymers.TABLE 5 Average pore Area ratio of Area ratio of Strength Color diameter(nm) coarse pores 1 (%) coarse pores 2 (%) (cN/dtex) ΔMR (%) propertyExample 14 20 or less 0 0 2.5 5.8 Excellent Example 15 20 or less 0 02.0 4.8 Excellent Example 16 45 0.5 — 2.0 5.1 Good Example 17 30 0 0 2.05.3 Excellent Example 18 30 0 0 3.3 5.0 Excellent Comparative — 5.0 —1.4 2.4 Failure Example 3 Comparative — 2.4 — 1.3 2.3 Failure Example 4Comparative — 4.6 — 1.3 2.3 Failure Example 5 Comparative — — — — — —Example 6Average pore diameter: Average pore diameter estimated based on TEMobservationArea ratio of coarse pores 1: Area ratio of pores having a diameter of200 nm or more to the total fiberArea ratio of coarse pores 2: Area ratio of pores having a diameter of50 nm or more to the total fiber

TABLE 6 Ratio in Average viscosity diameter Sea-part Islands- betweenArea of Thermal polymer part sea and Kneading ratio islands Strength U %Shrinkage Type wt % polymer islands procedure (%) (nm) Spinnability(cN/dtex) (%) (%) Example 14 N6 80 PET1 1.1 EXT 0.1 or 18 Good 4.1 1.212 less Example 15 N6 50 PET2 0.2 EXT 0.1 or 25 Good 3.1 1.8 12 lessExample 16 N6 50 PET3 0.3 EXT 5 143 Fair 3.3 2.5 10 Example 17 N6 80 PAO0.3 EXT 1.3 80 Good 3.5 1.5 12 Example 18 N6 80 PLA 0.7 EXT 0.1 or 80Good 4.0 1.3 12 less Comparative N6 50 PET4 0.9 chip 10 150 Failure — 10— Example 3 Comparative N6 70 PET5 0.9 chip 8 125 Failure — 9.1 —Example 4 Comparative N6 77 PET6 0.9 chip 14 80 Failure 2.7 9.3 —Example 5 Comparative PET4 75 N6 1.1 chip 10 — Failure — 11 — Example 6Area ratio: Area ratio of coarsely aggregated polymer particles having adiameter of 200 nm or more to the total islandsPET1: PET copolymerized with 5% by mole of 5-sodiosulfoisophthalic acidPET2: PET copolymerized with 12% by mole of 5-sodiosulfoisophthalic acidand 26% by mole of isophthalic acidPET3: PET copolymerized with 7% by mole of isophthalic acid and 4% bymole of an ethylene oxide adduct of bisphenol APET4: PET copolymerized with 2.5% by mole of 5-sodiosulfoisophthalicacid and 3.5% by mole of an ethylene oxide adduct of bisphenol APET5: PET copolymerized with 4.5% by mole of 5-sodiosulfoisophthalicacid and 8.5% by weight of PEG 4000PET6: Homopolyethylene terephthalatePAO: Polyalkylene oxide modified product (polymer soluble in hot water)EXT: Twin-screw extrusion-kneaderChip: Chip blending

Example 19

The melt spinning and draw thermal treatment procedure of Example 8 wasrepeated, except for using N66 instead of N6, setting the spinningtemperature at 280° C., and using 80% by weight of N66 and 20% by weightof the copolymerized PET. The yarn could be satisfactorily spun withoutany yarn breaking during continuous spinning for 24 hours. The crosssection of the polymer alloy fiber was observed under a TEM, to findthat the fiber was free from coarsely aggregated polymer particles, thearea ratio of islands each having a diameter of 200 nm or more to thetotal islands was 0.1% or less, and the area ratio of islands eachhaving a diameter of 100 nm or more was 1% or less. The TEM observationof the longitudinal section of the fiber shows that the islands has alined structure. The yarn had excellent physical properties as shown inTable 8.

The polymer alloy fiber was subjected to circular knitting and alkalitreatment by the procedure of Example 10, to remove 99% or more of thecopolymerized PET, to thereby obtain a round braid comprising ananoporous N6 fiber.

The cross section of the nanoporous N66. fiber was observed under a TEM,to find that the pores were unconnected pores, the average diameter ofthe pores was 10 to 20 nm and were free from coarse pores each having adiameter of 50 nm or more.

The round braid comprising the nanoporous N66 fiber was dyed and wasfound to have excellent color property. The nanoporous N66 fiber hadexcellent physical properties as shown in Table 7.

Example 20

A total of 80% by weight of a homopolyethylene terephthalate having amelting point of 255° C., an intrinsic viscosity of 0.63 and a meltviscosity of 830 poises (280° C., 2432 sec⁻¹) and 20% by weight of thepolymer soluble in hot water used in Example 17 were subjected to meltkneading at 275° C. using a twin-screw extrusion-kneader by theprocedure of Example 1, to thereby obtain polymer alloy pellets havingb* of 3.2. The kneaded product was subjected to melt spinning by theprocedure of Example 10, except for setting the temperature of themelting section 2 at 280° C. and the spinning temperature at 280° C. andchanging the discharge rate per orifice and the number of spinneretorifices. The fiber showed good spinnability and did not cause yarnbreaking during continuous spinning for 24 hours. The article was thensubjected to draw thermal treatment by the procedure of Example 10,except for setting the temperature of the first hot roller 24 at 90° C.,to obtain a 90 dtex, 36-filament polymer alloy fiber having a strengthof 3.3 cN/dtex, an elongation percentage of 40%, a U % of 1.5% and athermal shrinkage of 7%. The cross section of the polymer alloy fiberwas observed under a TEM (FIG. 25), to find that the fiber was free fromcoarsely aggregated polymer particles, the area ratio of islands eachhaving a diameter of 200 nm or more to the total islands was 0.1% orless, and the area ratio of islands each having a diameter of 100 nm ormore was 0.1% or less. The dark region corresponds to the PET, and thebright regions correspond to the polymer soluble in hot water. The TEMobservation of the longitudinal section of the fiber shows that theislands has a lined structure. The yarn had excellent physicalproperties as shown in Table 8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 8 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain a round braid comprising a nanoporous PET fiber.

The cross section of the nanoporous PET fiber was observed under a TEM(FIG. 26), to find that the average diameter of the pores was 20 nm andwere free from coarse pores each having a diameter of 50 nm or more. Inthe figure, the dark region corresponds to the PET, and the brightregions correspond to pores, and the pores are unconnected pores. Thephysical properties of the nanoporous fiber are shown in Table 7.

The round braid comprising the nanoporous PET fiber was dyed and wasfound to have excellent color property.

Example 21

The melt kneading procedure of Example 20 was repeated, except forchanging the temperature at 255° C. and using, instead of thehomopolyethylene terephthalate, a copolymerized PET being copolymerizedwith 8% by weight of PEG 1000 and 7% by mole of isophthalic acid andhaving a melting point of 235° C., an intrinsic viscosity of 0.65 and amelt viscosity of 920 poises (280° C., 2432 sec⁻¹)). The resultingpolymer alloy pellets had b of 3.8. The pellets were subjected to meltspinning by the procedure of Example 19, except for setting thetemperature of the melting section 2 at 255° C., the spinningtemperature at 255° C., and using a spinneret having orifices with aY-shaped profile. The pellets showed good spinnability and did not causeyarn breaking during continuous spinning for 24 hours. The kneadedproduct was subjected to draw thermal treatment by the procedure ofExample 20 to thereby obtain a polymer alloy fiber having a trefoilprofile. The cross section of the polymer alloy fiber was observed undera TEM, to find that the fiber was free from coarsely aggregated polymerparticles, the area ratio of islands each having a diameter of 200 nm ormore to the total islands was 0.1% or less, and the area ratio ofislands each having a diameter of 100 nm or more was 1% or less. The TEMobservation of the longitudinal section of the fiber shows that theislands has a lined structure. The yarn had excellent physicalproperties as shown in Table 8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 20 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain a round braid comprising a nanoporous PET fiber.

The cross section of the nanoporous PET fiber was observed under a TEM,to find that the average diameter of the pores was 20 nm and were freefrom coarse pores each having a diameter of 50 nm or more. The TEMobservation shows that the pores are unconnected pores. The physicalproperties of the nanoporous fiber are shown in Table 7.

The round braid comprising the nanoporous PET fiber was dyed and wasfound to have excellent color property.

Examples 22 and 23

Materials were subjected to melt kneading, melt spinning and drawthermal treatment by the procedure of Example 20, except for using,instead of the copolymerized PET, a polytrimethylene terephthalate (PTT)having a melting point of 220° C. and a melt viscosity of 1290 poises(280° C., 2432 sec⁻¹) or a polybutylene terephthalate (PBT) having amelting point of 220° C. and a melt viscosity of 550 poises (280° C.,2432 sec⁻¹). The cross sections of the polymer alloy fibers wereobserved under a TEM, to find that the fibers were free from coarselyaggregated polymer particles, the area ratio of islands each having adiameter of 200 nm or more to the total islands was 0.1% or less, andthe area ratio of islands each having a diameter of 100 nm or more was1% or less. The TEM observation of the longitudinal sections of thefibers shows that the islands has a lined structure. The yarns hadexcellent physical properties as shown in Table 8.

The polymer alloy fibers were subjected to circular knitting by theprocedure of Example 20 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain round braid each comprising a nanoporous polyester fiber.

The cross sections of the nanoporous polyester fibers were observedunder a TEM, to find that the average diameter of the pores was 20 nmand were free from coarse pores each having a diameter of 50 nm or more.The TEM observation shows that the pores are unconnected pores. Thephysical properties of the nanoporous fibers are shown in Table 7.

The round braids comprising the nanoporous polyester fibers were dyedand were found to have excellent color property.

Example 24

Materials were subjected to melt kneading by the procedure of Example20, except for using, instead of the PET, the polylactic acid (PLA) usedin Example 18 and setting the melting temperature at 220° C. The kneadedproduct was subjected to melt spinning by the procedure of Example 20,except for setting the temperature of the melting section 2 at 220° C.and the spinning temperature at 220° C. In this procedure, the articlecould be spun satisfactorily without any yarn breaking during continuousspinning for 24 hours. The resulting article was subjected to drawingand thermal treatment by the procedure of Example 10, except for settingthe temperature of the first hot roller 16 at 90° C. The cross sectionof the polymer alloy fiber was observed under a TEM, to find that thefiber was free from coarsely aggregated polymer particles, the arearatio of islands each having a diameter of 200 nm or more to the totalislands was 0.1% or less, and the area ratio of islands each having adiameter of 100 nm or more was 1% or less. The TEM observation of thelongitudinal section of the fiber shows that the islands has a linedstructure. The yarn had excellent physical properties as shown in Table8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 20 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain a round braid comprising a nanoporous PLA fiber.

The cross section of the nanoporous PLA fiber was observed under a TEM,to find that the pores were unconnected pores, have an average diameterof 20 nm and were free from coarse pores each having a diameter of 50 nmor more. The physical properties of the nanoporous fiber are shown inTable 7.

The round braid comprising the nanoporous PLA fiber was dyed and wasfound to have excellent color property. Regular PLAs do notsatisfactorily take up dyes, but the nonporous PLA fiber exhibits animproved uptake of dyes and shows higher color property than regular PLAfibers. In addition, the nanoporous PLA fiber has an increased surfacearea and thereby shows an increased rate of biodegradation as comparedwith regular PLA fibers and is optimal for medical applications in whichrapid bioabsorptivity is required.

Examples 25 and 26

Materials were subjected to melt kneading, melt spinning, draw thermaltreatment by the procedure of Example 20, except for using, instead ofthe PLA, a polypropylene (PP) or a polymethyl methacrylate (hereinaftermay be referred to as “PMMA”). The cross sections of the resultingpolymer alloy fibers were observed under a TEM, to find that the fiberswere free from coarsely aggregated polymer particles, and the arearatios of islands each having a diameter of 200 nm or more to the totalislands were 1.2% and 0.8%, respectively. The TEM observation of thelongitudinal section of the fiber shows that the islands has a linkedstructure. The yarn had excellent physical properties as shown in Table8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 20 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain round braids comprising a nanoporous PP fiber or ananoporous PMMA fiber. The pores in these fibers were connected pores.The physical properties of the nanoporous fibers are shown in Table 7.

Example 27

Materials were subjected to melt kneading by the procedure of Example20, except for using, instead of the PET, a polymethylpentene(hereinafter may be referred to as “PMP”) and setting the meltingtemperature at 255° C. The kneaded product was subjected to meltspinning by the procedure of Example 20, except for setting thetemperature of the melting section 2 at 255° C. and the spinningtemperature at 255° C. In this procedure, the article could be spunsatisfactorily without any yarn breaking during continuous spinning for24 hours. The resulting article was subjected to drawing and thermaltreatment by the procedure of Example 10, except for setting thetemperature of the first hot roller 24 at 90° C. The cross section ofthe polymer alloy fiber was observed under a TEM, to find that the fiberwas free from coarsely aggregated polymer particles, and the area ratioof islands each having a diameter of 200 nm or more to the total islandswas 1.0%. The TEM observation of the longitudinal section of the fibershows that the islands has a lined structure. The yarn had excellentphysical properties as shown in Table 8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 20 and treated with hot water at 100° C. for onehour to remove 99% or more of the polymer soluble in hot water, tothereby obtain a round braid comprising a nanoporous PMP fiber.

The cross section of the nanoporous PMP fiber was observed under a TEM,to find that the pores were unconnected pores, had an average diameterof 35 nm, and the area ratio of coarse pores each having a diameter of50 nm or more to the total pores was 0.6%. The physical properties ofthe nanoporous fiber are shown in Table 7.

Example 28

Materials were subjected to melt kneading by the procedure of Example20, except for using, instead of the PET and the polymer soluble in hotwater, a polyphenylene sulfide (hereinafter may be referred to as “PPS”)and the N6 used in Example 1, respectively, using PPS in an amount of90% by weight, and setting the temperature at 305° C. The kneadedproduct was subjected to melt spinning by the procedure of Example 20,except for setting the temperature of the melting section 2 at 305° C.and the spinning temperature at 305° C. and changing the discharge rateper one orifice and the number of spinneret orifices. Broken endoccurred twice during continuous spinning for 24 hours. The resultingarticle was subjected to drawing and thermal treatment by the procedureof Example 10, except for setting the temperature of the first hotroller 24 at 90° C., to obtain a 150 dtex, 48-filament polymer alloyfiber. The cross section of the polymer alloy fiber was observed under aTEM, to find that the fiber was free from coarsely aggregated polymerparticles, and the area ratio of islands each having a diameter of 200nm or more to the total islands was 1.5%. The TEM observation of thelongitudinal section of the fiber shows that the islands has a linedstructure. The yarn had excellent physical properties as shown in Table8.

The polymer alloy fiber was subjected to circular knitting by theprocedure of Example 20 and treated with formic acid for 2 hours toremove 99% or more of the N6, to thereby obtain a round braid comprisinga nanoporous PPS fiber. The pores were unconnected pores. The physicalproperties of the nanoporous fiber are shown in Table 7. TABLE 7 AreaArea Average ratio of ratio of pore coarse coarse diameter pores 1 pores2 Strength Color (nm) (%) (%) (cN/dtex) property Example 19 20 or less 00 2.2 Excellent Example 20 20 0 0 2.0 Excellent Example 21 20 0 0 2.0Excellent Example 22 20 0 0 2.0 Excellent Example 23 20 0 0 2.0Excellent Example 24 20 0 0 2.0 Excellent Example 25 38 0 0.8 1.8 —Example 26 32 0 0.6 1.5 — Example 27 35 0 0.6 1.7 — Example 28 50 1.4 —3.6 —Average pore diameter: Average pore diameter estimated based on TEMobservationArea ratio of coarse pores 1: Area ratio of pores having a diameter of200 nm or more to the total fiberArea ratio of coarse pores 2: Area ratio of pores having a diameter of50 nm or more to the total fiber

TABLE 8 Ratio in Average viscosity diameter Sea-part Islands- betweenArea of Thermal polymer part sea and Kneading ratio islands Strength U %Shrinkage Type wt % polymer islands procedure (%) (nm) Spinnability(cN/dtex) (%) (%) Example N66 80 PET1 0.9 Static 0.1 or 33 Good 4.1 1.213 19 less Example PET7 80 PAO 0.9 EXT 0.1 or 40 Good 3.3 1.5 7 20 lessExample PET8 80 PAO 1.0 EXT 0.1 or 38 Good 3.4 1.5 9 21 less Example PTT80 PAO 1.4 EXT 0.1 or 34 Good 3.1 1.7 10 22 less Example PBT 80 PAO 0.6EXT 0.1 or 45 Good 3.1 1.8 9 23 less Example PLA 80 PAO 0.6 EXT 0.1 or35 Good 2.9 1.8 9 24 less Example PP 80 PAO 1.0 EXT 1.2 40 Good 2.7 2.26 25 Example PMMA 80 PAO 1.0 EXT 0.8 35 Good 2.5 2.4 — 26 Example PMP 80PAO 1.0 EXT 1.0 38 Good 2.6 2.3 9 27 Example PPS 90 N6 1.0 EXT 1.5 52Fair 5.3 2.1 — 28Area ratio: Area ratio of coarsely aggregated polymer particles having adiameter of 200 nm or more to the total islandsPET7: Homopolyethylene terephthalate (η = 0.63)PET8: PET copolymerized with 8% by weight of PEG 1000 and 7% by mole ofisophthalic acidPAO: Polyalkylene oxide modified product (polymer soluble in hot water)EXT: Twin-screw extrusion-kneaderStatic: Static mixer (104 × 10⁴ splits)

Example 29

Materials were subjected to melt spinning and draw false-twisting by theprocedure of Example 1, except for changing the number of spinneretorifices and the discharge rate, to thereby obtain a 95 dtex,68-filament false-twisted yarn of N6/copolymerized PET alloy. This yarnhad excellent physical properties of a strength of 2.7 cN/dtex, anelongation percentage of 22%, a thermal shrinkage of 8%, a U % of 1.0%and a CR of 38%, and was free from not-untwisted portions and had goodcrimping quality. The cross section of the crimped polymer alloy yarnwas observed under a TEM to find that the yarn had an islands-in-seastructure comprising N6 as a sea (dark region) and the copolymerized PETas islands (bright region). The islands had an average diameter of 25nm, showing that the polymer alloy fiber comprised the copolymerized PETultrafinely dispersed. The area ratio of islands each having a diameterof 200 nm or more to the total islands was 0.1% or less, and the arearatio of islands each having a diameter of 100 nm or more was 0.9%. Theislands were dispersed as lines. A polyurethane fiber yarn “LYCRA”(registered trademark) available from OPELONTEX CO., LTD. was coveredwith this as a sheath yarn. The covered yarn was formed into a knitfabric for tights and was subjected to alkali treatment by the procedureof Example 1, to thereby obtain a knit fabric for tights comprising ananoporous N6 fiber. The knit fabric for tights had a METSUKE (mass perunit area) of 100 g/m² and contained 95% by weight of the nanoporous N6fiber and 5% by weight of the polyurethane fiber yarn. This wassubjected to treatment with silicone and fabric massaging. The knitfabric for tights was sawn to obtain tights. The TEM observation of thenanoporous N6 fiber sampled from the tights shows that the fiber wasfree from coarse pores having a diameter of 50 nm or more, and theaverage diameter of the pores was 25 nm. The pores were unconnectedpores. The yarn strength was 2.5 cN/dtex. The tights had good colorproperty and a high ΔMR of 5.6%, exhibited a delicate touch and freshhands like a skin and felt good to wear. The combination use of thepolyurethane fiber yarn imparts high stretchability and improvesdimensional stability of the tights upon washing.

Example 30

“LYCRA” was covered by the procedure of Example 28 with the polymeralloy fiber prepared according to Example 6. The resulting yarn wasformed into a short panty. The TEM observation of the nanoporous N6fiber sampled from the short panty shows that the fiber was free fromcoarse pores having a diameter of 50 nm or more, and the averagediameter of the pores was 25 nm. The pores were unconnected pores. Theyarn strength was 2.5 cN/dtex. The tights had good color property and ahigh ΔMR of 5.6%, exhibited a delicate touch and fresh hands like a skinand felt good to wear. The short panty had an ammonia adsorbing rate of55%. The combination use of the polyurethane fiber yarn imparts highstretchability and improves dimensional stability of the short pantyupon washing.

Example 31

Materials were subjected to melt spinning by the procedure of Example 1,except for changing the discharge rate per orifice and the number oforifices, to obtain a 400 dtex, 96-filament fiber of a N6/copolymerizedPET polymer alloy. The polymer alloy fiber had a strength of 2.5cN/dtex, an elongation percentage of 100% and a U % of 1.2%. The crosssection of the highly oriented undrawn polymer alloy yarn was observedunder a TEM, to find that the fiber was free from coarsely aggregatedpolymer particles, the area ratio of islands each having a diameter of200 nm or more to the total islands was 0.1% or less, the area ratio ofislands each having a diameter of 100 nm or more to the total islandswas 1% or less, and the islands had an average diameter of 33 nm. Thisarticle was subjected to draw false-twisting using a device shown inFIG. 29 by the procedure of Example 6, to obtain a 333 dtex, 96-filamentfalse-twisted yarn. The resulting false-twisted yarn had a strength of3.0 cN/dtex, an elongation percentage of 30%, a U % of 1.5% and a CR of33%. The cross section of the fiber of the crimped polymer alloy yarnwas observed under a TEM, to find that the fiber was free from coarselyaggregated polymer particles, the area ratio of islands each having adiameter of 200 nm or more to the total islands was 0.1% or less, andthe area ratio of islands each having a diameter of 100 nm or more was0.1% or less. The islands had an average diameter of 27 nm and had alined structure.

The false-twisted yarn was subjected to soft twisting of 300 turns permeter and used as warp and weft-in an S-twist/Z-twist two ply yarn tothereby obtain a 2/2 twill woven fabric. The twill woven fabric wassubjected to an alkali treatment by the procedure of Example 6, tothereby obtain a drapery fabric comprising a nanoporous N6 fiber andhaving a METSUKE (mass per unit area) of 150 g/m². The TEM observationof the nanoporous N6 fiber sampled from the drapery fabric shows thatthe fiber was free from coarse pores having a diameter of 50 nm or more,and the average diameter of the pores was 25 nm. The pores wereunconnected pores. The yarn strength was 2.5 cN/dtex.

The resulting curtain had good color property and a high ratio ofmoisture adsorption (ΔMR) of 5.5%, indicating sufficient hygroscopicity.A curtain was prepared from this fabric and was hanged in a six-mattatami room. The curtain served to make a fresh indoor environment bypreventing dewing due to its high hygroscopicity and adsorbing malodorgases. Thus, the nanoporous fibers of the present invention are suitablefor products for interior with better responsibility to environmentsthan that of conventional equivalents. The curtain was washed anddewatered in a washing net using a domestic washer but did not lose itsshape, showing that the curtain had good dimensional stability in spiteof its high hygroscopicity and high water adsorptivity, in contrast torayon curtains.

Example 32

Materials were subjected to melt spinning by the procedure of Example10, except for changing the discharge rate per orifice and the number oforifices and using Y-shaped discharge orifices. The spun yarn was woundat a rate of 900 meters per minute, subjected to two-step drawing at adraw ratio in the first step of 1.3 and a total draw ratio of 3.5,crimped by using jet nozzles and wound as a 500 dtex, 90-filament bulkedyarn having 9 crimps per 25 mm. The bulked yarn had a strength of 5.0cN/dtex and an elongation percentage of 25%. The cross section of thefiber of the crimped polymer alloy yarn was observed under a TEM, tofind that the fiber was free from coarsely aggregated polymer particles,the area ratio of islands each having a diameter of 200 nm or more tothe total islands was 0.1% or less, and the area ratio of islands eachhaving a diameter of 100 μm or more was 1% or less. The islands had anaverage diameter of 30 nm and had a lined structure.

Two plies of the resulting bulked yarn were doubled and subjected tofirst twisting (200 T/m), and two plies of the first-twisted yarn weresecondarily twisted (200 T/m), subjected to twist setting by dry heatingat 170° C. and tufted into a cut-pile carpet according to a conventionalprocedure.

The tufting herein was carried out according to a regular level cut bycontrolling the stitch so as to have a gauge of 1/10 and a METSUKE (massper unit area) of 1500 g/m². The tufted article was then subjected tobacking. In the tufting, a woven base fabric using a blended yarn of anacrylic fiber and a polyester fiber was used as the base fabric. Onlythe cut-pile portion was subjected to alkali treatment, to allow thecut-pile portion to be a nanoporous N6 fiber. This was observed under aTEM and was found to be free from coarse pores having a diameter of 50nm or more, in which the average diameter of the pores was 30 nm. Thepores were unconnected pores. The cut pile drawn therefrom had astrength of 2.0 cN/dtex. The cut-pile portion had good color propertyand a high ΔMR of 5.3%, i.e., sufficient hygroscopicity and could yielda fresh indoor environment as the curtain according to Example 31.

Example 33

Materials were spun by the procedure of Example 10, except for changingthe spinneret and the discharge rate per orifice, the resulting yarn waswound by the first take-up roller 8, doubled and received by a bunker.The yarns in the bunker were subjected to gathering to obtain a tow of15×10⁴ dtex. The tow was drawn in a water tank at 90° C. at a draw ratioof 3.2. The drawn tow was passed through a crimper, to which an oil wasfed, and was cut. The resulting cut fiber had a single yarn fineness of4 dtex, number of crimp of 10 per 25 mm and a fiber length of 51 mm. Thecut fiber had a strength of 3.3 cN/dtex and an elongation percentage of40%. The cross section of the fiber was observed under a TEM, to findthat the fiber was free from coarsely aggregated polymer particles, thearea ratio of islands each having a diameter of 200 nm or more to thetotal islands was 0.1% or less, the area ratio of islands each having adiameter of 100 nm was 1% or less. The islands had an average diameterof 33 nm and had a lined structure.

The cut fiber was separated using a carding machine and was formed intoa web using a cross lap weaver. The article was then subjected to needlepunching (1500/cm²) to obtain a fiber entangled nonwoven fabric of 150g/m². The nonwoven fabric was subjected to alkali treatment by theprocedure of Example 10, to thereby obtain a nonwoven fabric comprisinga nanoporous N6 fiber. The nanoporous fiber sampled from the nonwovenfabric was observed under a TEM and was found that the fiber was freefrom coarse pores having a diameter of 50 nm or more, and the averagediameter of the pores was 30 nm. The pores were unconnected pores. Thecut fiber itself was subjected to alkali treatment and was convertedinto a nanoporous fiber. The resulting nanoporous fiber had a strengthof 2 cN/dtex. The nonwoven fabric had good color property and highhygroscopicity in terms of ΔMR of 5.8%.

Example 34

The cut fiber comprising the polymer alloy prepared according to Example33 was spun to obtain a spun polymer alloy yarn. By using this as a warpand weft, a plain fabric having a METSUKE (mass per unit area) of 150g/m² was prepared. The plain fabric was subjected to alkali treatment bythe procedure of Example 10, to obtain a fabric comprising a nanoporousN6 fiber. The TEM observation of the nanoporous fiber sampled from thefabric shows that the fiber was free from coarse pores having a diameterof 50 nm or more, and the average diameter of the pores was 30 nm. Thepores were unconnected pores. The spun yarn of the nanoporous fibersampled from the fabric had a strength of 2.0 cN/dtex. The fabric hadgood color property, exhibited sufficient hygroscopicity in terms of ΔMRof 5.8% and good color property.

Example 35

A nonwoven fabric comprising a polymer alloy fiber and having a METSUKE(mass per unit area) of 35 g/m² was prepared by spinning in the samemanner as in Example 25, taking a yarn by an air sucker, separatingfibers and collecting on a net, and subjecting the collected yarn tocalendar rolling. The fiber taken by the air sucker had a single yarnfineness of 2 dtex. The spinning rate determined based on the finenesswas 4500 meters per minute. The cross section of the polymer alloy fibersampled from the nonwoven fabric was observed under a TEM, to find thatthe fiber was free from coarsely aggregated polymer particles, the arearatio of islands each having a diameter of 200 nm or more to the totalislands was 0.1% or less, and the area ratio of islands each having adiameter of 100 nm was 1% or less. The islands had an average diameterof 31 nm and had a lined structure.

The nonwoven fabric was subjected to treatment with hot water to therebyobtain a nonwoven fabric comprising a nanoporous PP fiber and havingexcellent water adsorptivity. The nanoporous fiber was sampled from thenonwoven fabric and was observed under a TEM to find that the fiber wasfree from coarse pores having a diameter of 50 nm or more hadunconnected pores as pores having an average diameter of 30 nm. As isdescribed above, the nanoporus fibers of the present invention areoptimal for yielding unprecedented high-performance nonwoven fabrics.

Example 36

Materials were subjected to melt spinning by the procedure of Example 1,except for changing the discharge rate and the number of spinneretorifices. Thus, 10 kg of a highly oriented undrawn yarn was wound. Theyarn comprised a polymer alloy of 90 dtex, 68 filaments having astrength of 2.7 cN/dtex, an elongation percentage of 100% and a U % of1.3%. The cross section of the polymer alloy fiber was observed under aTEM to find that a copolymerized PET was homogeneously dispersed withsize on the order of nanometers as particles having an average diameterof 20 nm, the area ratio of coarse islands each having a diameter of 200nm or more was 0.1% or less, and the area ratio of islands each having adiameter of 100 nm or more was 1% or less (FIG. 27). The observation ofthe longitudinal section shows that the copolymerized PET had a linedstructure.

The package had a good shape without saddle or yarns dropping at a sideof a cheese package. The package showed less water swelling thanarticles comprising regular nylon fibers, and was free from packagedeformation with time and had good dimensional stability. A highlyoriented undrawn yarn comprising a regular nylon undergoes waterswelling during winding, cannot be stably wound and fails to obtain apackage comprising a highly oriented undrawn yarn and having anelongation percentage of 70% to 200%. The nylon yarn cannot be subjectedto combined false twisting as in PET. In contrast, the nylon polymeralloy fibers of the present invention can stably yield a wound highlyoriented undrawn yarn having an elongation percentage of 70% to 200% andcan thereby be subjected to various yarn processing.

Comparative Example 8

The N6 used in Example 1 alone was subjected to melt spinning by theprocedure of Example 36. However, the resulting yarn swelled as a resultof water adsorption and elongated during winding, which invited unstablewinding and frequent burst of yarn.

Example 37

The highly oriented undrawn yarn prepared according to Example 36 and a70 dtex, 34-filament regular drawn N6 yarn being prepared separately andhaving a strength of 6 cN/dtex and an elongation percentage of 45% weresubjected to combined false-twisting at a draw ratio of 1.02 and aheater temperature of 165° C. The resulting combined false-twisted yarnhaving a CR of 25% was subjected to the procedure of Example 1 to form around braid, and the round braid was subjected to alkali treatment.

The nanoporous N6 fiber was sampled from the resulting round braid wasobserved under a TEM to find that the fiber was free from coarse poreshaving a diameter of 50 nm or more, and the average diameter of thepores was 10 to 20 nm, the yarn strength was 2.5 cN/dtex, and the poreswere unconnected pores. The fabric had good color property andsufficient hygroscopicity in terms of ΔMR of 4.5% and showed excellenthands with a soft and delicate touch. Thus, fabrics having excellenthands and being optimum for clothing can be obtained by the combinationuse of the polymer alloy fiber of the present invention and otherfibers.

In particular, conventional nylons do not yield highly oriented undrawnyarns having a high elongation to fail to provide further improvedhands. In contrast, fabrics having excellent hands can be easilyobtained according to the present invention, as is shown in thisexample.

Example 38

The polymer alloy fiber prepared according to Example 13 and a 70 dtex,96-filament regular N6 fiber were subjected to air yarn mixing using aninterlacing nozzle. A plain fabric having a METSUKE (mass per unit area)of 150 g/m² was prepared by using the resulting yarn as warp and weft,and subjected to alkali treatment by the procedure of Example 10 andthereby yielded a fabric comprising a nanoporous N6 fiber and a regularN6.

The nanoporous N6 fiber was observed under a TEM to find that the fiberwas free from coarse pores having a diameter of 50 nm or more, theaverage diameter of the pores was 10 to 20 nm, the yarn strength was 3.3cN/dtex, and the pores were unconnected pores. The fabric had good colorproperty and sufficient hygroscopicity in terms of ΔMR of 4%. The fabrichad excellent hands with a soft and delicate touch.

Example 39

A 2/2 twill woven fabric having a METSUKE (mass per unit area) of 150g/m² by using the crimped polymer alloy yarn prepared according toExample 1 as a warp and a 72 dtex, 27-filament viscose rayon as a weft.The fabric was then subjected to alkali treatment by the procedure ofExample 1.

The nanoporous N6 fiber was sampled from the resulting fabric and wasobserved under a TEM to find that the fiber was free from coarse poreshaving a diameter of 50 nm or more, the average diameter of the poreswas 20 nm or less, and the yarn strength was 2.5 cN/dtex. The pores wereunconnected pores. The fabric had good color property and sufficienthygroscopicity in terms of ΔMR of 7%. The fabric had excellent handswith a soft and delicate touch. Thus, the fabrics comprising thenanoporous fiber of the present invention in combination with otherfibers have further improved hands and/or hygroscopicity and are optimumfor fabrics for use in high-grade clothing.

Example 40

The polymer alloy cut fiber prepared according to Example 33 and cottonwere subjected to spinning of mixed cut fibers in a weight ratioof.50%/50% to obtain a blended yarn containing a polymer alloy fiber. Aplain fabric was prepared by the procedure of Example 34, except forusing the blended yarn, and was subjected to alkali treatment by theprocedure of Example 1. The fabric had good color property andsufficient hygroscopicity in terms of ΔMR of 4.8%.

The spun yarn comprising a nanoporous N6 fiber sampled from the fabrichad a strength of 2.0 cN/dtex. The nandporous N6 fiber was sampled andwas observed under a TEM to find that the fiber was free from coarsepores having a diameter of 50 nm or more, and the average diameter ofthe pores was 30 nm. The pores were unconnected pores.

Example 41

The fabric comprising the nanoporous PET fiber prepared according toExample 20 was allowed to adsorb triphenyl phosphate serving as a flameretardant (“REOFOS TPP” available from Ajinomoto Fine-Tech Co., Inc.) at20% owf (based on the weight of the fabric), a liquor ratio of 1:40, atemperature of 130° C. for one hour. The resulting article was washedwith water, subjected to soaping with an aqueous sodium carbonatesolution at 80° C. and subjected to domestic cleaning ten times. Theresulting fabric had a coverage of 7% by weight and showed goodself-extinguishing in a flammability test. Thus, the nanoporous fibersof the present invention can take functional materials therein to form a“capsulated structure”, serve to improve washing resistance and areoptimum as raw yarns which are good for treating with functionalmaterials.

Comparative Example 9

A regular PET fabric was subjected to flame retardation by the procedureof Example 41. The resulting fabric had a coverage of 1% by weight aftercleaning ten times and showed no self-extinguishing in a flammabilitytest.

Example 42

The fabric comprising the nanoporous PET fiber prepared according toExample 20 was allowed to adsorb a moisture absorbent “SR1000” (10%water dispersion) available from Takamatsu Oil & Fat Co., Ltd. at 20%owf of the moisture absorbent in terms of solid content, a liquor ratioof 1:20, a temperature of 130° C. for one hour. The resulting PET fabricshowed a degree of uptake of 12% or more and had excellenthygroscopicity in terms of ΔMR of 4% or more, which is equivalent to orhigher than cotton. Thus, the nanoporous fibers of the present inventioneasily take functional materials therein to form a “capsulatedstructure”, serve to improve the degree of uptake of the functionalmaterials and are optimum as raw yarns which are good for treating withfunctional materials.

Comparative Example 10

A regular PET fabric was subjected to moisturizing by the procedure ofExample 42. The resulting fabric, however, had a degree of uptake of themoisture absorbent of about 0% and exhibited no hygroscopicity.

Example 43

The fabric comprising the nanoporous PET fiber prepared according toExample 20 was allowed to adsorb a squalane. Such a squalane is anaturally-occurring oil component extracted from shark liver and servesas a substance having skin-care functions by the action of moisturizing.The treatment was carried out by dispersing a mixture containing 60% ofthe squalane and 40% of an emulsifier in water in a concentration of 7.5grams per liter and dipping the fabric therein at a liquor ratio of1:40, a temperature of 130° C. for 60 minutes. After the treatment, thefabric was washed at 80° C. for 2 hours. The coverage of the squalanewas 21% by weight to the resulting fabric. The fabric after domesticcleaning 20 times had a coverage of the squalane of 12% by weight to thefabric and exhibited sufficient washing (laundry) durability.

The round braid comprising the nanoporous PET fiber bearing the squalanewas formed into socks. Ten subjects suffering from dry ankle weresubjected to a wearing test for one week. As a result, eight subjectswere mitigated in dry skin. This is probably because the squalanetrapped by the pores was gradually extracted by the action of the sweatof the subject and was brought into contact with the skin.

Comparative Example 11

A regular PET fabric was subjected to exhaustion (uptake) by theprocedure of Example 43. The coverage after washing was 21% by weight tothe fabric, but that after domestic cleaning ten times was 0% by weight,showing no washing resistance.

Example 44

The fabric comprising the nanoporous N6 fiber prepared according toExample 10 was immersed in de-ionized water and was mixed with1,2-bis(trimethoxysilyl)ethane, followed by stirring for 3 hours. Afterstanding still at room temperature for 14 hours, the article was stirredfor further 13 hours, left stand for 14 hours and stirred for further 7hours for polymerizing silica. The round braid was washed withde-ionized water and was air-dried. This procedure yielded N6/silicacomposite material in the form of a fabric prepared by using the poresof the N6 nanofiber as a template. This material was an excellentmaterial having sufficient rigidity and flexibility and was a hybridmaterial having excellent flame retardancy. The composite materialcontained 30% by weight of silica.

Thus, the nanoporous fibers of the present invention can be easilyformed into hybrid materials by adsorbing a polymerizable monomer oroligomer and polymerizing the monomer or oligomer and are optimum asprecursors for advanced materials including organic materials havingfunctions of inorganic substances (e.g., flame retardancy or catalyticactivity) or inorganic materials having flexibility.

Example 45

The tights comprising the nanoporous N6 fiber prepared according toExample 29 was immersed in “New Policain Liquid” available from TAIHOPharmaceutical Co., Ltd. and was dried. This yielded tights that canrelease an agent for dermatophytosis by the action of the sweat.Patients with dermatophytosis were allowed to wear the tights one perday. This treatment was continued for one month to find that the symptomwas remedied because of sustained-released agent for dermatophytosis.Thus, the nanoporous fibers of the present invention are capable ofmedicinally efficacious components and are suitable as medical devices.

Example 46

The fabric comprising the nanoporous N6 fiber prepared according toExample 1 was immersed in a 3% aqueous diethylenetriamine solution at50° C. for one minute to allow the nanoporous N6 fiber to supportdiethylenetriamine. The acetaldehyde adsorbing capability of theresulting article was determined in the same way as that for ammonia. Asa result, the article showed excellent elimination capability, since theconcentration was decreased from 30 ppm to 1 ppm within 10 minutes.Thus, the nanoporous fibers of the present invention are capable ofsupporting adsorbents and are suitable as industrial materials typicallyfor chemical filters and air filters.

Example 47

A highly oriented undrawn yarn was prepared by melting the polymer alloyprepared according to Example 1 as a core component, and the N6 used inExample 1 as a sheath component respectively at 270° C., spinning at atemperature of 275° C. to obtain core-in-sheath multi-component fiberand taking the yarn at a rate of 3800 meters per minute. This wassubjected to draw false-twisting by the procedure of Example 1. Thecompounding ratio of the polymer alloy was 80% by weight. The resultingcrimped yarn comprising the core-in-sheath conjugated fiber was of 150dtex and 76 filaments and had a strength of 4.1 cN/dtex, an elongationpercentage of 27%, a U % of 1.0%, a thermal shrinkage of 10% and a CR of45%. The islands parts copolymerized PET in the polymer alloy as thecore component had an average diameter of 26 nm and were homogeneouslydispersed with size on the order of nanometers. The area ratio of coarseislands each having a diameter of 200 nm or more to the total islandswas 0.1% or less, and the area ratio of coarse islands each having adiameter of 100 nm or more to the total islands was 1% or less. Theislands-part polymer was dispersed as lines. The crimped yarn comprisingthe core-in-sheath conjugated fiber was subjected to circular knittingby the procedure of Example 1 and was subjected to alkali treatment, tothereby obtain a round braid comprising a nanoporous N6 fiber.

The nanoporous fiber was sampled from the round braid and was observedunder a TEM to find that the fiber was free from coarse pores having adiameter of 50 nm or more, and the average diameter of the pores was 20nm. The area ratio of nanopores was 77% of a cross section of the fiber.The nanoporous fiber had a yarn strength of 3.3 cN/dtex, higher thanthat in Example 1, and exhibited superior wear resistance. The poreswere unconnected pores. The fabric exhibited higher color property thanthat in Example 1 and had sufficient hygroscopicity in terms of ΔMR of4.8%.

Example 48

The core-in-sheath multi-component fiber spinning and drawfalse-twisting procedures of Example 47 were carried out, except forinterchanging the core component and the sheath component and settingthe compounding ratio of the polymer alloy at 50% by weight, to obtain acrimped yarn comprising a core-in-sheath conjugated fiber of 150 dtex,76 filaments having a strength of 4.1 cN/dtex, an elongation percentageof 27%, a U % of 1.0%, a thermal shrinkage of 10% and a CR of 45%. Theislands of the copolymerized PET in the polymer alloy as the sheathcomponent had an average diameter of 26 nm and were homogeneouslydispersed with size on the order of nanometers. The area ratio of coarseislands each having a diameter of 200 nm or more to the total islandswas 0.1% or less, and the area ratio of coarse islands each having adiameter of 100 nm or more to the total islands was 1% or less. Theislands-part polymer was dispersed as lines. The crimped yarn comprisingthe core-in-sheath conjugated fiber was subjected to circular knittingand alkali treatment by the procedure of Example 47, to thereby obtain around braid comprising a nanoporous N6 fiber. The nanoporous fibersampled from the round braid was observed under a TEM to find that thefiber was free from coarse pores having a diameter of 50 nm or more, andthe average diameter of the pores was 20 nm. The area ratio of nanoporesto the cross section of the fiber was 45%. The nanoporous fiber had ahigher strength of 3.5 cN/dtex than that in Example 1. The pores wereunconnected pores. The fabric had good color property and sufficienthygroscopicity in terms of ΔMR of 4%.

Example 49

The multi-component fiber spinning procedure of Example 48 was carriedout, except for using the high-viscosity N6 used in Example 14 as the N6alone side, and the polymer alloy prepared in Example 1 as the polymeralloy side, to obtain a side-by-side yarn at a compounding ratio of 50%by weight/50% by weight. The high-viscosity N6 had a viscosity as largeas 2 times or more that of the polymer alloy. The resulting undrawn yarnwas subjected to drawing at a draw ratio of 1.2 and thermal treatment bythe procedure of Example 10, to obtain a 110 dtex, 34-filament crimpedside-by-side yarn having a strength of 4.1 cN/dtex, an elongationpercentage of 27%, a U % of 1.2%, a thermal shrinkage of 10%, number ofcrimp of 20 per 25 mm. The islands of the copolymerized PET in thepolymer alloy as the outside component of the crimp had an averagediameter of 26 nm and were homogeneously dispersed with size on theorder of nanometers. The area ratio of coarse islands each having adiameter of 200 nm or more to the total islands was 0.1% or less, andthe area ratio of coarse islands each having a diameter of 100 nm ormore to the total islands was 1% or less. The islands-part polymer wasdispersed as lines. The resulting crimped side-by-side yarn wassubjected to circular knitting and alkali treatment by the procedure ofExample 48, to thereby obtain a round braid comprising a nanoporous N6fiber. The nanoporous fiber was sampled from the round braid and wasobserved under a TEM to find that the fiber was free from coarse poreshaving a diameter of 50 nm or more, and the average diameter of thepores was 20 nm. The area ratio of nanopores to the cross section of thefiber was 44%. The yarn had a high strength of 3.5 cN/dtex. The poreswere unconnected pores. The fabric had good color property andsufficient hygroscopicity in terms of ΔMR of 4%. The fabric showedfurther higher bulkiness after water adsorption.

Example 50

The multi-component fiber spinning and draw thermal treatment proceduresof Example 49 were carried out, except for using the low-viscosity N6used in Example 1 as the N6 alone side and the polymer alloy prepared inExample 14 as the polymer alloy side, to thereby obtain a 110 dtex,34-filament crimped side-by-side yarn having a yarn strength of 4.0cN/dtex, an elongation percentage of 25%, a U % of 1.2%, a thermalshrinkage of 10% and a number of crimp of 18 per 25 mm.

The islands of the copolymerized PET in the polymer alloy as the insidecomponent of the crimp were dispersed with an average diameter of 18 nm,and the area ratio of coarse islands each having a diameter of 100 nm ormore to the total islands was 0.1% or less. The resulting crimpedside-by-side yarn was subjected to circular knitting and alkalitreatment by the procedure of Example 49, to thereby obtain a roundbraid comprising a nanoporous N6 fiber.

The nanoporous fiber was sampled from the round braid and was observedunder a TEM to find that the fiber was free from coarse pores eachhaving a diameter of 50 nm or more, and the average diameter of thepores was 20 nm. The area ratio of nanopores to the cross section of thefiber was 45%. The nanoporous fiber had satisfactory bulkiness and ahigh yarn strength of 3.4 cN/dtex. The pores were unconnected pores. Thefabric exhibited good color property and had sufficient hygroscopicityin terms of ΔMR of 4%. The fabric exhibited further improved airpermeability after water adsorption, since crimps elongated and stitcheswere enlarged.

Example 51

The round braid comprising the polymer alloy fiber prepared in Example10 was treated with a 2% aqueous sodium hydroxide solution (95° C.,liquor ratio of 1:40) for twenty minutes to decompose and dissolve out50% of the copolymerized PET in the polymer alloy fiber with a weightloss as the fiber of 10%. The dissolution proceeded in the form of arind from the fiber surface layer, and the area ratio of nanopores tothe cross section of the fiber was 50%. This portion was observed undera TEM to find that the pores were unconnected pores having-an averagediameter of 20 nm, and there was no coarse pores each having a diameterof 50 nm or more.

The round braid had a ΔMR of 4.0% and an ammonia adsorbing rate of 50%,showing excellent hygroscopicity and/or adsorptivity, and exhibited asufficient percentage of water retention of 6.0%. The nanoporous fiberalso showed reversible water swelling but a higher dimensional stabilityunder wet conditions in terms of a percentage of swelling of 4% thanthat in Example 10. The fiber, had a higher yarn strength of 3 cN/dtexthan in Example 10.

Example 52

A high-density plain fabric having a METSUKE of 170 was prepared byusing the crimped polymer alloy yarn prepared in Example 1 as a warp andweft. The article was subjected to alkali treatment by the procedure ofExample 1, to obtain a plain fabric comprising a nanoporous N6 fiber.The shape and physical properties of the nanoporous fiber sampled fromthe plain fabric were determined and were found to be similar to thosein Example 1. The article was buffed to fibrillate the surface layer ofthe nanoporous fiber and to form a multitude of fibrils having adiameter of about 0.01 to 1 μm which covered the surface of the wovenfabric. The resulting fabric had a soft touch and feeling like spun,exhibited water repellency although it had not been coated and wassuitable as a sporting fabric.

Comparative Example 12

A high-density plain fabric was prepared and was subjected to buffing bythe procedure-of Example 51, except for using a false-twisted regular N6yarn (77 dtex, 34 filaments). The resulting fabric, however, was notsufficiently fibrillated and failed to provide fibrils covering thesurface of the woven fabric and to obtain a soft and “spun feel” touch.The fabric was further buffed to proceed fibrillation but resulted inbreakage.

Example 52

A five-ply back satin of 180 g/m² was prepared by using the crimpedpolymer alloy yarn prepared in Example 1 as a weft and a regular N6fiber (44 dtex, 12 filaments) as a warp. The article was subjected toalkali treatment by the procedure of Example 1, to obtain a back satinwoven fabric comprising a nanoporous N6 fiber. The shape and physicalproperties of the nanoporous fiber sampled from the fabric weredetermined and were found to be similar to those in Example 1. Thearticle was buffed to fibrillate the surface layer of the nanoporousfiber and to form a multitude of fibrils having a diameter of about 0.01to 1 μm which covered the surface of the woven fabric. The fibrils werefurther separated by water punching. The resulting fabric was suitableas a fabric for wiping cloths.

Example 53

The nonwoven fabric comprising the nanoporous N6 fiber prepared inExample 33 was buffed to obtain a multitude of fibrils having a diameterof about 0.01 to 1 μm, which covered the surface of the nonwoven fabric.The resulting fabric had a surface touch near to the skin, unlikeconventional nylon nonwoven fabrics.

Example 54

The nonwoven fabric comprising the nanoporous PP fiber prepared inExample 35 was buffed to obtain a multitude of fibrils having a diameterof about 0.01 to 1 μm, which covered the surface of the nonwoven fabric.This article was more suitable as a filter than conventional PP spunbond nonwoven fabrics.

INDUSTRIAL APPLICABILITY

The porous fibers according to the present invention serve todramatically the liquid adsorptivity and/or adsorptivity which theyinherently have, as intact or as fibrous structures such as yarns, cutfibers, felts, packages or fibrous articles using the fibers. They canhave a variety of functions using the nanoporous structure, arepromising in various fields and are very epoch making.

More specifically, the fibers easily take a variety of functionalmaterials in the nanopores and are easily processed to have thefunctions, as compared with conventional fibers.

The fibers can bear or support, for example, any of moisture absorbents,flame retardants, water repellents, humectants, cold insulators, heatinsulators and lubricating agents in the form of, but not limited to,fine particles. In addition, agents for promoting health and beautycare, such as polyphenols, amino acids, proteins, capsaicin andvitamins, as well as agents for dermatosis such as dermatophytosis andmedicaments such as disinfectants, anti-inflammatory agents andanalgesics.

Further, polyamines, photocatalytic nanoparticles and other agents foradsorbing and/or decomposing harmful substances can be imparted to thefibers. If desired, hybrid materials can be arbitrarily obtainedtherefrom by allowing the fibers to adsorb or absorb organic orinorganic monomers capable of forming polymers and polymerizing themonomers.

The fibers can have selective adsorptivity and/or catalytic activity byactivating the walls of the pores by chemical processing using theirhigh specific surface areas.

The fibers can have any of various functions as mentioned above withadjustable performance according to necessity, can yield comfortableproducts for use in clothing such as panty hose, tights, inner wears,shirts, blousons, trousers and coats and can also be used in clothingmaterials such as cups and pads; interior decoration such as curtains,carpets, mats and furniture; livingwares such as wiping cloths;industrial materials such as abrasive cloths; and vehicle interiordecoration.

The fibers, if adsorbing any functional molecule or agent, can also beused as most advanced materials typically in the fields of environment,medical or information technology (IT), such as fibrous structures ashealth-cosmetic-related goods, base fabrics for medicaments and medicaldevices, as well as electrodes of fuel cells.

1. A porous fiber containing pores each having a diameter of 100 nm orless, wherein the area ratio of pores each having a diameter of 200 nmor more to the total cross section of the fiber is 1.5% or less, andwherein the pores are unconnected pores.
 2. A porous fiber containingpores each having a diameter of 100 nm or less, wherein the area ratioof pores each having a diameter of 200 nm or more to the total crosssection of the fiber is 1.5% or less, wherein the pores are connectedpores, and wherein the fiber has a strength of 1.0 cN/dtex or more. 3.The porous fiber according to claim 1, wherein the area ratio of poreseach having a diameter of 50 nm or more to the total cross section ofthe fiber is 0.1% or less.
 4. The porous fiber according to claim 1,wherein the pores have an average diameter of 5 to 30 nm.
 5. The porousfiber according to claim 1, wherein the porous fiber is partiallyfibrillated to have fibrils each having a diameter of 0.001 to 5 μm. 6.The porous fiber according to claim 1, wherein the porous fiber iscrimped.
 7. The porous fiber according to claim 1, wherein the porousfiber has a strength of 1.5 cN/dtex or more.
 8. The porous fiberaccording to claim 1, comprising 80% by weight or more of a polyester orpolyamide.
 9. The porous fiber according to claim 1, wherein the porousfiber has a ratio of moisture adsorption (ΔMR) of 4% or more.
 10. Theporous fiber according to claim 1, wherein nanopores are unevenlydistributed at cross section of a fiber, and wherein the area ratio ofthe nanopores to the total cross section of the fiber is 30% or more.11. A yarn or cut fiber comprising the porous fiber according to claim 1or 2 in combination with one or more other fibers.
 12. A fibrous articleat least partially comprising the porous fiber according to claim 1 or2.
 13. A fibrous article comprising the porous fiber according to claim1 in combination with one or more other fibers.
 14. The fibrous articleaccording to claim 12, which is a woven fabric, a knitted fabric or anonwoven fabric.
 15. The fibrous article according to claim 11, which isselected from clothing, products for interior, livingwares andindustrial materials.
 16. The fibrous article according to claim 11,comprising one or more functional materials.
 17. A polymer alloy fiberhaving an islands-in-sea structure and comprising a lower solublepolymer as a sea part; and a higher soluble polymer as islands parts,the islands constituting a lined structure, wherein the area ratio ofislands each having a diameter of 200 nm or more to the total islands is3% or less.
 18. The polymer alloy fiber according to claim 17, whereinthe area ratio of islands each having a diameter of 100 nm or more tothe total islands is 1% or less.
 19. The polymer alloy fiber accordingto claim 17, wherein the islands have an average diameter of 1 to 100nm.
 20. The polymer alloy fiber according to claim 17, wherein theislands have an average diameter of 10 to 50 nm.
 21. A polymer alloyfiber comprising two or more polymers having different solubilities,wherein the polymers having different solubilities constitute a layeredstructure at cross section of a fiber, wherein higher soluble polymerlayers have an average thickness of 1 to 100 nm, and wherein a layeredstructure comprising higher soluble polymer layers having a linedstructure at longitudinal section of a fiber occupies 50% or more of thearea of a cross section of the fiber.
 22. The polymer alloy fiberaccording to claim 17, wherein the content of the islands-part polymeris 10 to 30% by weight of the total fiber.
 23. The polymer alloy fiberaccording to claim 17, wherein the higher soluble polymer is a polymereasily soluble in an alkaline solution.
 24. The polymer alloy fiberaccording to claim 17, wherein the fiber has an Uster unevenness of 0.1to 5%.
 25. The polymer alloy fiber according to claim 17, wherein thefiber has an elongation percentage of 70 to 200%.
 26. The polymer alloyfiber according to claim 17, wherein the fiber has a CR as an indicatorof crimp properties of 20% or more, or the number of crimp is 5 or moreper 25 mm.
 27. The polymer alloy fiber according to claim 17, which is aconjugated fiber comprising a polymer alloy and one or more otherfibers.
 28. A yarn or a cut fiber comprising the polymer alloy fiberaccording to claim 17 or 21 and one or more other fibers andconstituting a combined filament yarn, a blended yarn or a blended cutfiber.
 29. A package or a felt, comprising the polymer alloy fiber ofclaim 17 or 21 or the yarn or cut fiber of claim
 28. 30. A fibrousarticle at least partially comprising the polymer alloy fiber of claim17 or
 21. 31. A fibrous article comprising the polymer alloy fiber ofclaim 17 in combination with one or more other fibers.
 32. The fibrousarticle according to claim 30, which is a woven fabric, a knitted fabricor a nonwoven fabric.
 33. Pellets of a polymer alloy comprising apolyamide and a polyester, wherein a dispersed polymer component isdispersed in an average diameter of 1 to 50 nm.
 34. The pelletsaccording to claim 33, wherein the area ratio of coarse particles of thedispersed polymer component having a diameter in terms of circle of 100nm or more at cross section of a pellet is 3% or less of the totaldispersed polymer particles at cross section of a pellet.
 35. Pellets ofa polymer alloy, comprising a polyamide and a polyester, containing 30to 90% by weight of a polyester copolymerized with 1.5 to 15% by mole ofa sulfonate and having an average weight of 2 to 15 mg.
 36. (canceled)37. Pellets of a polymer alloy, comprising a polymer selected frompolyamides, polyesters and polyolefins; and a polyetherester beingsoluble in hot water, wherein the content of the polyetherester is 10 to30% by weight, and wherein the pellets have a b* value as an indicatorof coloring of 10 or less.
 38. A method for melt-spinning a polymeralloy fiber, comprising the steps of weighing and feeding a lowersoluble polymer and a higher soluble polymer independently to atwin-screw extrusion-kneader, melting and blending the polymers in thetwin-screw extrusion-kneader to form a polymer alloy, and melt-spinningthe polymer alloy, wherein the spinning is carried out so as to satisfythe following conditions (1) to (3): (1) the content of the highersoluble polymer in the polymer alloy is 5 to 60% by weight; (2) theratio in melt viscosity of the lower soluble polymer to the highersoluble polymer is 0.1 to 2; and (3) the length of a kneading section ofthe twin-screw extrusion-kneader is 20 to 40% of the effective length ofscrews.
 39. A method for melt-spinning a polymer alloy fiber, comprisingthe steps of weighing and feeding a lower soluble polymer and a highersoluble polymer independently to a static mixer having a number ofsplits of 100×104 or more, melting and blending the polymers in thestatic mixer to form a polymer alloy, and melt-spinning the polymeralloy, wherein the spinning is carried out so as to satisfy thefollowing conditions (4) and (5): (4) the content of the higher solublepolymer in the polymer alloy is 5 to 60% by weight; and (5) the ratio inmelt viscosity of the lower soluble polymer to the higher solublepolymer is 0.1 to
 2. 40. A method for melt-spinning a polymer alloyfiber comprising a lower soluble polymer and a higher soluble polymer,comprising storing and dry-blending two or more different pellets in ablending tank before melting of the pellets, feeding the dry-blendedpellets to a melting section, and blending and melt-spinning thedry-blended pellets, wherein the spinning is carried out so as tosatisfy the following conditions (6) to (8): (6) the content of thehigher soluble polymer in the fiber is 5 to 60% by weight; (7) the ratioin melt viscosity of the lower soluble polymer to the higher solublepolymer is 0.1 to 2; and (8) the blending tank can contain 5 to 20 kg ofpellets.
 41. The method for melt-spinning a polymer alloy fiberaccording to any one of claims 38 to 40, wherein the content of thehigher soluble polymer in the resulting blend is 10 to 30% by weight.42-47. (canceled)